Google Webmaster Tools ‘Links To Your Site’ Number Reduces? You’re not alone!

Really, you are not alone and you do not need to take any actions.

Some Webmaster Tools users have reported missing data in the “Links to your site” section. We are aware of this issue and are looking into it; you do not need to take any action. We hope to have the normal data shown again in the near future. The data shown there is informational and does not affect your site’s crawling, indexing or ranking.

source Google Webmaster Help Forum Announcements