A Google Webmaster Help thread has reports of some webmasters claiming their Google Webmaster Tools impression data dropped to zero on December 28th/29th.

Why do I think this is a reporting error over a webmaster error?

Gary Illyes from Google responded in a way that made me believe it was a bug with Google’s reporting engine:

Webmaster Stuart said:

Others have seen the same issue.

Have you?

Forum discussion at Google Webmaster Help.