For hackathon 5.0, I made this Friend Finder, so you can find your friends... It should be pretty simple to use, just type in a supported URL below into the text field and choose where you want to find your friends.
The most important thing to have on a social networking site, like the ones supported here, is obviously friends. You may be following a bunch of people on Twitter but not so many on Yelp and that sucks but I can fix that. And since I am able to suggest friends, I am also able to suggest people you should invite - should could be incredibly baller and mildly creepy ALL AT ONCE, with no external authentication required.
List of supported services: