You gotta be kidding about not seeing fixed gears in Brooklyn, right?
I walked out of some sushi place on 5th the other night and the first 5 bikes I saw, either locked up or riding were all fixed. Coming out of Prospect Park from a run on Saturday morning, I saw a couple of guys all on fixed gears chilling by the farmer's market. I think the only place with a higher concentration of fixed gears than Brooklyn is the East Village/Lower East Side. Everyone I see there is on a fixed.
It's great.