Most lists are topically focused, and while most interesting ones also have a community aspect, pure community-oriented discussion is usually at least somewhat apologetic. On lists that understand the concept of community, off-topic posts are tolerated, but there tend to be "OT:" subject lines and stuff like that. On many other lists, pure community-oriented discussion simply isn't tolerated, which weakens their utility. Of course, the inverse problem is that, if the community-oriented discussion completely drowns out the topical stuff, the list can lose focus and drift into irrelevance.
That's not the case on LJ. Since the "topic" for any given blog is the person writing it, there just isn't the sense of shame at speaking about whatever matters to you. And that often comes much closer to the definition of the community (or communities) that the author is in...
