The problem inevitably becomes what do you do once the community has become larger? How do you keep the topics and the level of discussion from sliding downward? This is an issue that Lambda the Ultimate's been facing for the last couple of years as less academic, more industry people join the community, and they've been handling it fairly well but it's taken a lot of work on everyone's part. Reddit's facing the same issue as well. If there are more dumb people than smart ones in a community, they can dictate what articles make it to the front page and overwhelm the good discussion with drivel.