A little shocking, since he was just assuring us a few weeks ago that the Android Marketplace would get better, among other upcoming Android hotness, but Android Senior Product Manager Erick Tseng is leaving Google for Facebook "to help innovate at the intersect of mobile and social." Which makes us slightly more excited for new Facebook stuff for phones—like being built into the iPhone OS—and a little sad about Android.

Given that he basically ran Android, it seems like Facebook's got some pretty big plans for mobile stuff. Think huge. [Twitter]