Internet fundamentalism doesn't actually work.

There's an antipattern that Internet social sites tend to: people get nostalgic for the old times, and think that if they can just get rid of these annoying newcomers they'll get the old site back again just like they remember. The primary fallacy is that the reason it was interesting back then was that nobody knew what they were doing and what would come next; attempting to encase that in carbonite is unlikely to achieve the desired effect. The secondary fallacy is that they themselves are different people now.

(thinking of two example sites going through precisely this angst right now. And of another, where a Usenet newsgroup from 15 years ago just revived itself on Facebook, and it appears to be working precisely because we're different people now so it's interesting again and we don't know what happens next.)

Edit: Now a slightly longer pontification.