Here are people who have contributed to Jackson JSON process development:
(version numbers in brackets indicate release in which the problem was fixed)

Tatu Saloranta, tatu.saloranta@iki.fi: author

Ryan Heaton, ryan@webcohesion.com: co-author

Peter Harris, Peter.Harris@betfair.com: contributor

Alain Penders:
  * Reported problem with JavaTypeMapper, where floating point numbers were
    accidentally converted to Booleans.
    [0.8]

Mike Eastey:
  * Reported problem with JavaTypeMapper had a bug which prevented custom
    mappers (as well as slower interface-based introspection) from working,
    provided path to specific underlying bugs.
    [0.8.2]

Augusto Callejas:
  * Reported problem with JavaTypeMapper (and JsonTypeMapper), which
    caused read operation not to handle EOF appropriately but instead
    cause a NullPointerException.
    [0.9]

Maciej Pestka:
  * JavaTypeMapper did not implicitly flush generator after mapping
    objects: it should, and now will (note: JsonTypeMapper not directly
    affected, flushing still needed)
    [0.9]

Tudor Bosman:
  * Symbol table handling not thread-safe
    [0.9.3]

Michael Mangeng:
  * Suggested [JACKSON-1]: make JsonNode implement Iterable<JsonNode> to
    allow use of Java 5 foreach loop with container nodes.
    [0.9.3]

Johannes Link:
  * Reported [JACKSON-8]: Serialization of BigDecimal broken with JavaTypeMapper
    [0.9.3]

Stanislaw Osinski:
  * Reported [JACKSON-14], contributed code to resolve it and improve
    generics-handling significantly.
    [0.9.4]
 	 
Michael Descher:
  * Reported [JACKSON-18], ArrayIndexOutOfBounds on IntNode, due to
    off-by-one problem with comparisons used for caching common values.
    [0.9.4]

Mike Goodwin:
  * Suggested [JACKSON-9]: Add support for (non-standard) Json comments.
    [0.9.4]

Ray Racine:
  * Pointed out [JACKSON-25]: Problems with Maven pom for lgpl version
    [0.9.4-backport]

Scott Dixon:
  * Contributed unit test (TestComplexJavaType) for verifying functioning
    of object serialization
    [0.9.5]
  * Suggested [JACKSON-38] Allow serializing/deserializing DOM trees (Node, Document)
    [1.4.0]
  * Suggested [JACKSON-45]: adding convenience methods to simplify writing
    custom serializers
    [1.0.0]

Justin Friedl:
  * Requested [JACKSON-52]: ability to disable getter method auto-detection
    [0.9.9]
  * Reported [JACKSON-53] (and suggested way to fix it): problem serializing
    iBatis bean classes generated (or wrapped) by CGLib. Probably would also
    have caused problems with Hibernate and other frameworks.
    [0.9.8]
  * Requested [JACKSON-61]: Allow suppressing writing of bean properties
    with null values
    [0.9.9-3]
  * Reported [JACKSON-62]: NPE with JsonMappingException
    [0.9.9]

Scott Anderson:
  * Suggested [JACKSON-48]: Integrate ObjectMapper with JsonGenerator,
    JsonParser; add MappingJsonFactory.
    [0.9.9]
  * Requested [JACKSON-84]: Add JsonGenerator.writeRawValue method(s).
    [0.9.9-3]

Kevin Grained:
  * Reported [JACKSON-58] (and suggested a fix): NPE with String[]
    serialization
    [0.9.9]

Eldar Abusalimov:
  * Reported [JACKSON-81]: Data binding code could lead to unnecessary
    blocking because it tried to advance parser (and stream) after binding
   [0.9.9-3]
  * Reported [JACKSON-99]: IOExceptions should not be wrapped during object
    mapping.
   [0.9.9-4]

Stephen Duncan jr:
  * Pointed out problem with JacksonJsonProvider where strict equality
    comparison was used instead of using MediaType.isCompatible().
   [0.9.9-4]

Ray Tsang:
  * Reported [JACKSON-103] (problem with Groovy class serialization),
    submitted fix
   [0.9.9-7]

Oleksandr Alesinskyy:
  * Reported [JACKSON-104], problems with packaging, build.
   [0.9.9-7]

Christoph Strebin:
  * Requested [JACKSON-105], proposed a way to implement it:
    Allow suppressing output of "default values"; which
    means value of a property when bean is constructed using the default
    no-arg constructor
   [1.1.0]

Peter Harris:
  * Reported [JACKSON-139], provided patch for fixing it: Non-numeric
    double values (NaN, Infinity) are serialized as invalid JSON tokens
    (reported by Peter H)
   [1.1.1]

Dan Simpson:
  * Reported [JACKSON-144]: Static "getter-like" methods mistaken for
    getters (for serialization)
   [1.1.2]

Gregory Gerard:
  * Reportd [JACKSON-143]: NPE on ArrayNode.equals() when comparing empty
    array node to non-empty array node
   [1.1.2]

Dain Sundstrom:
  * Suggested addition of "-use" for javadoc generation
   [1.2.0]
  * Suggested [JACKSON-136] JsonParser and JsonGenerator should implement
    java.io.Closeable (since they already have close() method)
   [1.2.0]

Gabe Schnaubelt:
  * Reported [JACKSON-155]: Failed to serialize java.io.File (with infinite
    recursion)
   [1.3.0]

Benjamin Darfler:
  * Suggested [JACKSON-164]: Improve null-handling in JsonGenerator.writeStringField()
   [1.3.0]
  * Suggested [JACKSON-165]: Add JsonParser.getBooleanValue() convenience method
   [1.3.0]

Troy Waldrep:
  * Reported [JACKSON-162]: OSGi packaging problems for xc package.
   [1.3.0]
 
Randy Layma:
  * Reported [JACKSON-171]: Self-referential types cause infinite recursion
    when using only JAXB annotation introspector
   [1.3.0]

Shay Banon:
  * Suggested [JACKSON-168] Make JsonLocation serializable (and deserializable)
   [1.3.0]

Brian McCallister:
  * Suggested [JACKSON-173]: Add "JsonParser.Feature.ALLOW_SINGLE_QUOTES"
    to handle commonly encountered invalid JSON content
   [1.3.0]
  * Reported [JACKSON-179] Single-long-arg factory Creators were not working
   [1.3.0]

Ted Bergeron:
  * Reported [JACKSON-177].
   [1.3.0]

Jeff Yu:
  * Suggested [JACKSON-180]: Add 'JsonParser.Feature.INTERN_FIELD_NAMES' to
    allow disabling field name intern()ing.
   [1.3.0]

Doug Daniels:
  * Suggested [JACKSON-176]: Add a work-around for Javascript's problems
    with big 64-bit longs (due to always representing numbers as 64-bit
    doubles internally, thus truncating some long values)
   [1.3.0]

Nick Padgett:
  * Reported [JACKSON-183]: Root-level 'JsonDeserialize' annotation
    not handled completely; 'as' setting was not taking effect
   [1.3.0]

Nathan Ching:
  * Reported [JACKSON-190]: Problem deserializing some nested generics
    types
   [1.3.1]

Martin Lauer:
  * Reported [JACKSON-194] ObjectMapper class loading issues on Android
   [1.3.1]

Edward Thorne:
  * Reported [JACKSON-197]: 2 debug message print out to System.err
   [1.3.1]

Steve Lopez:
  * Reported [JACKSON-200]: java.sql.Date deserialization not working well
   [1.3.1]
  * Reported [JACKSON-203]: Date deserializers should map empty String to null
   [1.3.1]

Mike Pilone:
  * Suggested [JACKSON-201]: Allow serialization of "empty beans" (classes
    without getters), if SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS is
    disabled; or if class has recognized Jackson annotation
   [1.4.0]
  * Reported [JACKSON-202]: Non-public fields not deserialized properly
    with JAXB annotations
   [1.3.1]

Stephen Friedrich:
  * Reported additional issues with [JACKSON-203]
   [1.3.2]

Jeff Schnitzer:
  * Reported [JACKSON-188]: problems running Jackson 1.3 on GAE, due
    to dependency to JAXB API classes
   [1.3.2]

Elliot Shepherd:
  * Reported [JACKSON-214], suggested fix: Enum types with subclasses
    fail to serialize
   [1.3.3]

Gil Markham:
  * Reported [JACKSON-196], suggested fix: Schema generation does not
    respect the annotation configured serializer on a bean property
   [1.4.0]

Mark Stevens:
  * Requested [JACKSON-208] Allow unquoted control characters (esp. tabs)
    in JSON Strings and field names
   [1.4.0]

Mike Rheinheimer:
  * Reported [JACKSON-216] Jackson JAXB annotation handler does not use
    @XmlElement.type property for figuring out actual type
   [1.4.0]

Chris Carrier:
  * Suggested [JACKSON-236]: Allow deserialization of timestamps-as-Strings
    (not just timestamps as JSON integer numbers).
   [1.5.0]

Andrei Voden:
  * Suggested [JACKSON-232]: Add 'SerializationConfig.Feature.DEFAULT_VIEW_INCLUSION'
    to disable inclusion of non-annotated properties with explicit views
   [1.5.0]

Lars Clausen:
  * Reported [JACKSON-246]: JAXB property name determination not working correctly.
   [1.5.0]
  * Reported [JACKSON-250]: Type name not always detected 
   [1.5.0]
  * Reported [JACKSON-251]: Concurrency bug in pre-1.5.0 version of
    @JsonSubTypes handling
   [1.5.0]

Pierre-Yves Ricay:
  * Requested [JACKSON-244]: allow private fields processing without having to annotate them
   [1.5.0]

John Lister:
  * Reported [JACKSON-256]: incorrect combining of serialization inclusion
    values; suggested better way to do it
   [1.5.0]

Gennadiy Shafranovich:
  * Reported [JACKSON-263]: BooleanNode.asToken() incorrectly returns 'true'
    token for all nodes (not just 'false' ones)
   [1.4.4, 1.5.0]

Fabrice Delhoste:
  * Reported [JACKSON-265]: problems with generic type handling for
    serialization
   [1.5.1]

Raymond Feng:
  * Reported [JACKSON-269]: missing OSGi export by mapper (o.c.j.m.jsontype.impl)
    needed by jackson-xc module
   [1.5.1]

Martin Tomko:
  * Reported [JACKSON-266] Deserialization from JsonNode fails
   [1.4.4, 1.5.2]

Lukasz Dywicki:
  * Reported [JACKSON-273] Problems with OSGi dependency declarations
   [1.5.2]

Brian Oberman:
  * Requested [JACKSON-289] Ability to serialize char[] values as JSON Arrays
    with String values of length 1 (and accepting these on deserialization)
   [1.6.0]

Paul R Brown:
  * Requested [JACKSON-193] Ability to use @JsonCreator and @JsonValue with
    enum types
   [1.6.0]

Ketan G:
  * Requested [JACKSON-300] Add 'JsonParser.Feature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER
    to allow non-standard character escapes like \'.
   [1.6.0]  

Rob Ottway:
  * Requested [JACKSON-301] Allow JsonMappingException to return name of "bad"
    (unrecognized) field
   [1.6.0]