This analysis is interesting but deeply flawed, as you're just using one variable. I don't think anyone would refer to OC as the most hipster place in America.
Weather is a huge missing component. Another is hilliness/other bike-friendliness (bike lanes, etc). The top 12 cities in the analysis are warm-weather cities (mostly California/Hawaii).
For example, no-one is buying bikes in Chicago at the moment, because it's freaking cold. But there are likely many more fixed-gear bikes here than almost anywhere else (flat, bike-friendly city with lots of hipsters). Portland is capital of hipsterdom - well atleast until Pittsburgh takes over (http://www.washingtonpost.com/blogs/arts-post/post/portlandi...) but it's cold there right now so people aren't selling their bikes.
I hosted chifg.com after the great bikeforums schism. And that was prior to lfgss.com. I also helped quite a few other cities get up and running with communities, probably about 15 or so.
The first was NYC though. They were the ones who after the BF schism set up an invite only community for fixed gear bikes.
Tracing earlier than that and you only find messengers/couriers riding them, go back to 1987 and you pretty much end up with 1 Toronto messenger and Buffalo Bill in London.
By the time I set up http://www.lfgss.com I already figured that the fixie thing was dead, but if anything it boomed afresh.
As trends go, I think it ceased to be fashion a while ago and became utility. It wouldn't have survived otherwise.
Admittedly this is just a guess, but might the Carson velodrome explain Orange County's dominance in this index? There's precious little overlap in the Venn diagram of people who race track bikes (on tracks) and people who ride track bikes because bike messengers ride track bikes.
Weather is a huge missing component. Another is hilliness/other bike-friendliness (bike lanes, etc). The top 12 cities in the analysis are warm-weather cities (mostly California/Hawaii).
For example, no-one is buying bikes in Chicago at the moment, because it's freaking cold. But there are likely many more fixed-gear bikes here than almost anywhere else (flat, bike-friendly city with lots of hipsters). Portland is capital of hipsterdom - well atleast until Pittsburgh takes over (http://www.washingtonpost.com/blogs/arts-post/post/portlandi...) but it's cold there right now so people aren't selling their bikes.