We’ve long been hearing rumors of voice calls within Facebook, possibly with some integration with Skype. Now a leaked picture seems to show a “Call” button appear in the Facebook messaging system. The button apparently appeared for a brief moment and was quickly removed from the menu. Skype and Facebook already have collaborated to merge VoIP functionality with the social network service, but so far there hasn’t been any integration of voice dialing directly in Facebook’s web-based service. Of course, if the call button leak is true, perhaps we’ve stumbled upon a hot upcoming feature.