I'm not suggesting that the "sky will fall", I'm suggesting that it is inevitable that this site will change if it continues to grow, user count wise. To suggest it hasn't evolved and changed from it's original state is disingenuous really. (Not that you are doing that, specifically)
Digg and reddit have turned into a glorified dorm room because that's what their average user is, a male college kid. Clearly, many people do feel the user base of this site changing - we wouldn't be commenting on this thread were this not the case.
It's not a good/bad thing, as it means you've chosen to broaden your base as opposed to remain niche. There's nothing wrong with that. But at some point, you hit the magical land where the average user demographic has changed so much that the tipping point is passed.