So, I did research on gay social networks a while back and it's an interesting problem. Anything that tries to be a legit social networking site and posture itself as not just for hookups doesn't do very well.
The biggest example is Fabulis. That was showing some promise, but it just wasn't going to be profitable in the way they needed it to be. The beta was well-loved and was supposedly a big support network for gay teens when the bullying stories went big. What they tended to find though is that acceptance was the biggest killer of an exclusively gay social site since more and more people were just find being out on Facebook and felt need for separating your friend communities became less. So, that site switched to Fab.com and started doing a daily deal thing instead.
I think Google+ could be a further killer to exclusively gay social networks since you can really customize your friend categories and who sees who and what. I think once G+ adds groups, you'll see a big movement of the old school Yahoo groups and the private gay groups on Facebook over there. Facebook has nice group functionality, but the lack of privacy options limits people joining and liking things. (A non-gay example is how a couple struggling to have kids wouldn't want FB listing that they just joined a group called "Thinking about In-Vitro").
The best two communities I've seen so far are RealJock and Gaymer since they organize around some broad interests that tend to rally the everyday gay guys who like being gay, but that might be secondary to what makes them unique.