I was skeptical of "Tsu" -- a social network with a business plan that ran to paying its members from ad revenues when they shared content -- but ran it in the social sidebar at KN@PPSTER for a bit. Sorry, it's just ... meh. And it's outta there.
I've replaced it with a real social network that's actually libertarian -- Liberty.me. That is NOT an "affiliate link." I won't be collecting a commission if you join. I'm promoting it because I like it. It's a paid service but they've brought their price down to a pretty damn reasonable $5 a month and I highly recommend it.
I'd call Liberty.me the libertarian version of Facebook, but it's actually more than that. In addition to the usual social network stuff (a profile, messaging/chat, etc.) you get your own Wordpress blog space and there are live events and so forth. And of course it's full of libertarians. But unlike a convention or whatever, when you get tired of a bunch of libertarians you can just open another browser tab instead of having to check out of your hotel and go somewhere else, if you know what I mean (and I think you do).