You may be right. In the large, I'm optimistic that it's possible to set up a forum where sensible discussion of hot button issues like politics is possible. Certainly, HN offers good initial conditions for achieving this: a great base of intelligent commenters who mostly seem able to have intelligent conversations with one another, even when they disagree. But maybe HN isn't the right place to be attempting this.
There are a few examples of online communities expanding so fast that original users no longer find them intellectually stimulating. Is there a single root cause? Are users so overconfident in their mutual abilities to discuss off-topic content safely, that they mistakingly end up allowing their own communities to kick themselves out; is it the fault of the design of the community software and system/processes; or, could it be that the community grew too quickly?
As somebody who enjoys this community a lot, I want to know that if 1,000 people start posting random URL's tomorrow, that not only would software filters stop junk from getting through, but that the community would step up and moderate itself because, albeit this is Hacker News, algorithms are never perfect: we are going to have to use our brains to make sure the site is still focused (or re-focused) regardless of how interesting an article might be.
On the other hand, there are good signs this may not necessarily happen to Hacker News. It's very possible that Digg, Reddit, and newcomer social news sites will be enough to satisfy the needs of most users. This site could be like a chess club in that it's open to everybody, but most people wouldn't care.
At the same time, one has to admit that if a social news site continues to address every topic on earth, it could get to the point where as the content becomes more similar to that of Digg or Reddit, there would be an exponential increase in new registrations daily of users looking for the next big thing. These users would then vote up new types of stories and change the site in a very short time. I think I read that one can't grow a team by more than 25% in number per year, or one will have a team that has lost qualities of the existing group--this is likely a major factor in retaining consistency and focus for this community, too.
