It seems that some people feel that it was foretold at Pubcon by Matt Cutts himself. During the time Matt was speaking, he suggested that an improvement of search quality occurred when there was a 10 to 15% reduction in authorship. Some thought that meant that Google reduced, or will reduce the amount of authrorship mark-up appearing in SERPs.
A column written by Dr. Peter J. Meyers explains in greater detail the situation of the drop in Google authorship, and asks if authorship counts dropped, which searches lost mark-up, and what can be done about it.
To read Dr. Petter’s full column, you can find it here, or by following the link below:
Google’s December Authorship Shake Up