In a city that's been flattened by more than a century of human development, but where you have to get up and down stairs all the time, it's a huge bonus not to have any added weight on a bike. For a lot of people who like to ride around but are disinterested in bike maintenance, a singlespeed or fixed gear bike (or 3-speed) is pretty much the most reliable and hassle-free you can make a bike.

I have friends who ride bikes everywhere here in NYC but don't know a thing about changing a flat or how to tighten up their brake cables. Believe me, for them, derailleurs just mean more potential for dysfunction.

I ride both, and though I like having gears for longer, varied-terrain rides, a fixed gear makes wonderful sense in the big city.

I actually got back into bikes a few years ago when a friend who's cycled his entire life explained his fixed gear to me. I became enamored of the idea of converting an older road bike, but from there, I found myself obsessed w/ all things C & V, randonneur bikes, etc. Obsessive or trendy fixed riders just make up another subculture or fad to me, like BMXers or downhillers or weekend roadies. They tend to be in the young and style-conscious demographic, but they're still only a small segment of a greater community of bike people of all types. (My own fascination among the crowd these days is the dorky, hardcore bike commuters, actually. The people who ride everywhere and have done so forever and who adamantly adhere to an aesthetic of a-stylishness in their bikes and bike wear. I have a friend like this: she rides her bike everywhere, it's almost glued to her, but she doesn't know the first thing about it, and I'd venture to guess, wouldn't even be able to tell me the brand name if asked. Start watching these types, and you forget the fixed fashionistas are even around, trust me.)