For the past year or so this place hasn't been "cliquey" at all, that seems to have died down a lot though you see remnants of it sometimes.
Clique really isn't the right term to use because it implies that the group has malicious intent. I don't think that the people who were in the cliques ever meant to exclude others or make anyone feel bad. Really they were just groups of close friends on the board who would have little conversations in different threads. This isn't so bad once in a while, you expect it on a message board, but when the same group of friends seems to come into nearly every thread and start joking with each other, it starts to get really annoying. Especially when the thread is a topic that you are genuinely interested in but instead of replies with any substance you get two pages of bantering between two or three posters that takes everything off-topic. It's true that if you wanted to join in and be included in the jokes that they would surely let you, they are all nice people. But the point, at least for me, was always that it wasn't really the time or place for personal conversations. That should be in PMs or in a thread dedicated to that purpose. When you have people spamming up legitimate topics it is frustrating and defeats the whole purpose of the board because instead of being able to discuss the topic at hand you have to sift through meaningless one-liners that have nothing to do with anything.
It happens in real life all the time. There are some people who you can't ever really have a serious conversation with because their answers will all be sarcastic, or sexual jokes, or taking a stab at their friends. It's funny at first but gets irritating very quickly.
But like I said, I think that this has died down quite a bit and isn't a problem really anymore. I can think of a few posters who are still like that, but the problem with online cliques is that you can't "out" them like you would in real life. In real life cliques are more defined, people know what group they belong to and that everyone else belongs to. But on a message board it's not really appropriate to start naming certain posters you think are being too spammy or having too many personal conversations. It just isn't good form. So the people who are being cliquey rarely actually realize that they are doing it, and then are shocked when all of a sudden other people start getting pissed at them, because in their minds they were just having a good time. And they were, and that's fine, but it needs to be done in their own arena and not in nearly every thread in a public forum. I don't think it excludes others, it just irritates them.