Just voted and although I do have accounts on most of the social networking sites listed (except for Linkedin), my favorite would have to be Facebook. I love those gaming apps and how easy it is to use the site although I don't like how they're continually making changes to it. lol
BTW, I think Yahoo 360 no longer exists. There is now Yahoo Profiles which have replaced it. :)
You could be right about Yahoo. I have trouble keeping up. I know each time I sign in it says, "Trina is...." then asks what I'm doing right now..kinda like twitter does.
I have facebook, also. My favorite is Twitter though. Maybe because I understand it better, seeing as how I had that before Facebook. lol