Facebook scans private messages to inflate the "Like" counter on websites
Facebook has confirmed that it’s registering all URL shares as Likes to a website. That means we’re all adding to a website’s Facebook Like glow, whether we want to or not, when we alert friends to URLs via private Facebook conversations.
Read more: Facebook scans private messages to inflate the "Like" counter on websites
Story added 8. October 2012, content source with full text you can find at link above.