n00b1 - 9:12 am on Feb 5, 2013 (gmt 0)
I've noticed the same... Except the links that have disappeared are the vast majority of links to my homepage and some of the more popular inner pages of my site. These are genuine natural backlinks.
I'm sure this has happened before. It coincides with the recent PR update so there may be some recalculation going on for that metric?
P.S. Checked the official WMT forums and it seems the issue has been noticed by several others and has been escalated to Google reps.