If nothing else, anyone who visits e.g. Silicon Valley and hangs out with geeks there, will quickly start picking out the "geek uniform". I find it funny when fellow geeks thinks they're clueless about fashion, and still manage to dress in very specific ways that makes them recognisable as a group. That is fashion, even if they're not following mainstream fashion.

The first time I visited the Bay Area, I stood out like a sore thumb because I didn't fit into "Bay Area geek fashion" (I dressed too "smart" because it was my first business trip abroad). I see that here in London too - e.g. if a developer comes into the office in a shirt, it tends to elicit comments. There are even small but noticeable differences between how the developers and designers dress.