Posted by Crell on February 26, 2013 at 6:49am
The REST team believes it's in Drupal's best interest to back off from supporting PUT requests directly in the rest.module. While it is still supportable by the core routing system, the semantics of PUT and the complexity of Drupal entities are just too incompatible to be viable at this time.
Feedback on this decision is welcome in the announcement thread until 4 March, but at this time we don't believe it is possible to support well.