Do we have cliques here? Absolutely. There are various collections of people here that will move as a pack through threads and against those they feel have slighted them, or a member of their group. But the catch here is that it's not a conscious thing. No one here sits there as they type and think "I'm a part of Group X" and act according to that. It's like mob mentality on a small scale. We have those on the site we most identify with and try to stick close to them/move in the direction they move. This is made easier because these groups form along lines of similar opinions/beliefs.
We had the liberal clique for a while...
We have the conservative clique still...
We had/have the "We Hate LW!" clique (this one comes and goes as they're eventually baited into crossing the line and getting exiled)
And there are probably a few I'm not hitting. They're never formal, and membership is typically open to anyone who shares the same core beliefs. They don't ask to join, they aren't invited (because afterall, no one does this knowingly most of the time), they just become part of that group.
But it is true, those who usually start railing against some grand conspiracy of "cliques" are the ones who haven't found their own group on the site, or who want instant acceptance. They're the ones who are fastest to claim administrative favoritism too. They're the ones who want to walk into a room and be king of the hill immediately.