When I first moved to California, I thought everyone was rude, because they don't wave or say "hi" to each other. I've since revised my thinking. In Rolla, I would wave at everyone that I saw on the 12 mile stretch from home to school. Of course, there weren't that many people there to begin with, and I figured they all lived in what we would call a neighborhood for the area. In general, they would wave back (with all five fingers). When I moved to my current location, I continued to do the same, but with fewer responses (at least, polite ones). I've unfortunately, pulled back my radius from home where I'll wave, but I think I've figured out the equation.

The Bay Area has refined their association with people with whom they feel a comradery. When I ride the motorcycle to work, every Harley rider waves at me. In fact, virtually every motorcyclist waves at me (sometimes the crotch-rocket riders snub me). I've even had bikers in oncoming traffic on the freeway (clear across the median) wave at me. I also drive a 3/4 ton diesel pickup. It is your typical contractor's vehicle for my area. Contractors wave at me when I go downtown, assuming I'm one of their own. Day Laborers saturate the local grocery store in the morning looking for work, and try to wave me down if Annie isn't with me, assuming I'm looking for helpers.

So, I've come to grips with my new belief that people here are not rude. I'ts just that the density of people is so incredible, they don't feel they have anything in common with the general population, and have to find something they feel a kinship for in order to be friendly. In the grocery store, no one says anything to each other, but I can't tell you how many people have pulled up next to me at a signal light and yelled "nice bike!"
Continually increasing my comfort level here...