It's that "too many places" thing that really causes the problem. I learned when I lived in Cincinnati that signaling a lane change just told people you were going to cut them off, so they'd speed up rather than letting you in. But in LA, you signal, bumper to bumper at 80 miles an hour, and they'll let you in.
Now mix these two very different styles of driving in one melting pot. And mix in the people who feel 10 miles over the speed limit is the way to drive on the freeway (I do), and the people who feel they need to police speeders and park themselves in the fast lane going 5 miles under the speed limit. Chaos reigns.
The thing that's really been bugging me lately are the two extremes of aggressive and overly polite drivers. They're both unpredictable and they both break the law. Really, even if you think it's nice to wave me through the intersection while I have a stop sign and you don't, you're not following the rules of the road.
I find this "nice driver" thing particularly annoying if I'm on my bicycle. I'm cleated into my pedals, and I don't do track stands really well. So if I'm coming to a stop, I can either take my foot out of the pedal and really stop, or time it so I know the intersection is clear. Predicting what that traffic is going to do is impossible when some people blast through and others slow down to "let the bicyclist go."
Of course, the other problem with the melting pot of drivers in Portland is when the weather changes. There are the people who have never seen snow who put the chains on and drive 10 miles an hour just because there's a prediction of snow. But on the other hand, there are people who have driven in snow all their lives, and don't realize that Portland gets soupy, untreated snow that gives you no traction whatsoever. I swear this is what happened a few weeks back when a half an inch of snow paralyzed the city for a night.
What to do about it? Complain in my blog, that's about all I can do as long as the government keeps assuming everyone should be able to operate 3,000 pounds of steel. I long for the days of science-fiction where automated pods take you everywhere you go, but then I'd probably bitch about people screwing that up too...