I agree with Tallulah. I've never found people here to be exclusive or unfriendly when I've initiated contact. In some cases they didn't know who I was before, in others they are not the sort to approach first, and in others it just took the extra push of being directly addressed or me introducing common ground that we have. Most people are kind of flattered when you notice them and you have something to say to them. I know I am always pleasantly surprised when that happens.
Most people that you may consider popular or well-known here have just invested time or effort into their friendships or associations on the forum, and so it is not unreasonable that that is where they would reap their rewards. I think it is easy to feel like "they wouldn't like me anyway", "they probably don't even know who I am", or "other people can fit in, but I can't and no one will ever notice me". I think these are largely products of your own thought processes, rather than reflecting other people's real thoughts or intentions. The catch is that if you continue thinking in those ways, it can result in self-defeating behaviours that make it more likely for those things to become true. You have more power over your situation than you think, so use it! Look outwards, and try to think about addressing other people's interests or needs and I think you may be surprised at the response!
Having said that, Vent is a place where there are a lot of regulars and it is one way of creating your own little subgroup that extends over into your forum life too.