Google has discontinued its Buzz service in lieu of Google+.  In the last several days, Google stopped accepting authorization for Buzz, so it no longer made sense for dlvr.it to continue supporting posts to Buzz.

For reference, here are Google's help pages and announcements regarding the Buzz service:

http://mail.google.com/support/bin/answer.py?hl=en&answer=1698228&topic=1669052

http://groups.google.com/group/google-buzz-api/t/dc21a377f92ef70e

For information regarding dlvr.it's support for Google+, please follow our post here.