The challenge, in my opinion, is that although they can be great for the communities, I think they come at a cost for entrepreneurs.
I've done a lot of things from a distance. After art school I moved away from the city to paint. I reasoned that doing so cut costs and that I could paint well anywhere. Years later I partnered in an interaction design firm in a small town employing a similar rationale. Most recently, we've been working on our startup from Vancouver, which is beautiful and a nice place to raise a family.
In each of these instances, the logic for being away from a center (be it art, design or startup) has been sound. Additionally, there are always strong proponents in these communities to keep people doing "great things close to home." No matter how strong the logic is though, it simply doesn't hold up. There are greater opportunities for those who put themselves at the heart of the "action".
You could likely start a great company in Pennsylvania, but even with low rent and more equity, you'd still have a weaker "deal". The appeal of YC, in my opinion, is that it's so close to where people think in startup-terms and is run by people who actually live in that world.
Although some will bemoan my saying so, the closer you can get to the action, the better. There are probably some great actors in Helsinki, but I bet you'll never hear anything about them.