Not that I am disagreeing but would you mind mentioning the social advantages that you are talking about?

Face to face conversations [http://headrush.typepad.com/creating_passionate_users/2006/0...], bars, theaters, museums, entertainment parks, turist attractions, easy shopping posibilities, etc.

There are many advantages to clustering together that electronics and increased communication simply cannot replace yet (and I doubt it ever will, even video calling feels "phony" somehow).

I'm sorry but I lived an extremely rural town for 10 years with <20k people and all of these thing were available. I'm not convinced these are exclusive to cities.

Where my grandparents live there is nothing, no school, no shops no bus stop, only a comunity center and a part time church.

20k is a town. 100 people is nothing.

Extremely rural is <500 people. No traffic lights, no Subway sandwiches. Just a country store, 7 churches, and 49 horses.

The ability to find a group of people like you. If you're straight, white, and born in the small town, this isn't a problem. As a gay man, I'd have a lot of trouble in many small towns.

The ability to walk down the street at 3 in the morning and see a non-trivial number of people around.

A friend was in a small town teaching for the summer, and he said "So then we went to the bar. I say the bar because there was only one." Where I live, there are 171 listed in the phone book.

Mass transit precluding the need to own a motorized conveyance, proximity to life's staples (and the varieties available thereof), diversity in culture and ideas (even ethnicity, if that's your bag), architectural variety (nothing beats looking at a giant skyscraper for wondering at the sheer human achievement).

It's all subjective, after all; but that's just off the top of my head.