My social media filters:
LinkedIn - if I recognize you or place you in information management, I'll connect.
Twitter - hey, you choose to follow me, I'll probably follow back.
Facebook - if I won't bail you out of jail, pick you up at the airport, help you move, or a few other very narrow exceptions, it ain't happening. Facebook is where the barriers go down just a little bit.
Google+ - yeah right. :P
Any other service, if you see this:
It's probably me and I'll probably connect. If you see a "jesse wilkins" that doesn't use that pic, it probably isn't.