Frosmo has the best use of social media for businesses I have seen to date - use Facebook connect to get people to log in to your site for A) a contest or B) some other benefit.
It's a natural way to leverage social media and try and get some visibility to your business in a way that seems natural and useful for the people involved. After all, who wants to have ANOTHER user name and password just to enter some contest or get customized info...
