Yeah, I've noticed (sorry for the generalization, I realize not everyone fits stereotypes, but this is just something I've noticed)
mtn bikers tend to be very hippish where I've been riding... Old "much loved" (beat up) gear, granola, pb&j, plain water, Clif products and honey (or Hammer). Organics, etc. Stringy vegan/veggie guys and gals with great smiles and dispositions. I've been offered 'to share a bowl' quite a bit (not that I've taken them up on it) but that's just the type...
Roadies tend to be more white-collar, high-dollar, fancy equipment-oriented. Friendly, but very much into their cadence, HR, speed, etc. Shiny, clean eq, look at you like you're going to burst into flames if you happen to pop off your bike downtown and share a beer and a smoke with a friend.
I'm not sure if it's that hippies aren't always as into 'speed' as they are into 'getting on trails'... or that they see their bikes as utilitarian modes of travel instead of an excercise habit/hobby?
I dunno. I'm too much of a wuss to actually do mtb racing (I'm afraid I'd break easily if I braked hardly) so I have a do-anything mtb frame with cushy shocks and thin-ish smooth tires. hybridisation?