Facebook

[skinsguy]

Originally Posted by NC_Skins

Instagram is my guess. It could be google + though. Facebook was out long before it became mainstream. You used to have a college email to even register if I recall.

Yes, you're absolutely right! And it went by that valid email address to put you in that college's Facebook network.

Instagram is owned by Facebook, so there's no real competition there. Google+ has been growing - especially because most everyone has either a Gmail account or an Android phone (or both.) A lot of my friends who don't have Facebook IM me through Google Hangouts.