I think it does attract those who are interested in community because it is immediately a dialogue (I've never done the boards so I'm not sure what sort of community that forms), but you come to LJ with a sense of participation and reciprocity as well as staking out your own personal corner. It's like moving into a co-op: you know the neighbors share at least a few basic interests, and what keeps it fun is learning how your interests diverge and intersect in other areas while still playing in the same playground that brought you together.