Human Contact in the City
Being an introverted in a big city actually works for me. For big cities lend themselves to lots of weak relationship ties; smaller settings would simultaneously mean more isolation and more depth in the relationships you did have. But there is something to be said for "the power of weak ties," a phrase Malcolm Gladwell uses in his book, "The Tipping Point." This article from Freakonomics explores the concept of relationship avoidance (people preferring ATMs to tellers or Amazon.com to Borders) and concludes that human contact is a good thing.
And I agree, and enjoy the many such interactions life in a big city offers: offering pleasantries to the SEPTA bus driver, cracking jokes with the day care receptionist, exchanging non-verbal cues with the people you hold a door open for, and so on and so on. Now, if I lived in a small town, all of these people would know my business, and I'm not sure I'd like that.
Yet another advantage, at least for me and my preferences, for life in a big city. Lots of weak ties, rather than either a deficit of human contact or a little too little breathing room. And lots of opportunities to turn a mundane intersection - at the bus stop, at day care, at the door - into a genuine human interaction.