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-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]
 
Troy Waldrep:
  * Reported [JACKSON-162]: OSGi packaging problems for xc package.
   [1.2.1]

Randy Layma:
  * Reported [JACKSON-171]: Self-referential types cause infinite recursion
    when using only JAXB annotation introspector
   [1.2.1]