Many consider YouTube.com a social network. To be honest, I never thought of it as one, but the reality is that users post content, and other users interact with that content. So it does act like a social network in that sense.

It's probably my personal situation that blocked the idea of it being a social network from my head, but I think of it as a "public place" - no private interaction for me on there, no interactions with people I know on there. Just interactions with strangers that create/share content.

YouTube

YouTube