Noticing some changes to your Google Webmaster Tools data? Don’t panic!
Over the past couple of days there have been an increasing number of reports about large decreases in the number of links reported in the ‘Links to your site’ section of WMT (by as much as 75% in some cases).
Judging from what affected webmasters are saying in the forums, the majority are confused by such large changes in the data. Others are flat out panicking “Where my all back link gone while I didn’t use ‘disavow links’ tool????”
Most recently in a Google Webmaster Help thread John Mueller from Google helped calm the crowd, stating that it appears to be a bug.
So the good news is it appears to be some kind of technical glitch, and the guys at Google are on the case.