People who seem to think that by turning on my blinker I am telling them to "Speed up"
ARGH!!!!!!!!!

-Josh
Oops, I forgot to mention to Josh - if anyone's trying to switch lanes, it's a violation to keep them from doing so.
At least in California.
-SKesselman
SO many people do this that I believe it is actually unintentional with some folks. It's as if when some people realize that someone else is passing them, they think, "Oh, I must have slowed down too much... let me pick up the pace." It just happens with far too many people to be spiteful. Or maybe I am giving too much credit where it ain't due?
Jim-J-Mac
I only see this when I change lanes to get away from them. If they speed up while you're clearly trying to go in front of them, then they're not only rude, but they're creating a major safety hazard.
I seem to encounter this when most often when I'm trying to get out of an 'exit only' lane on the freeway.
After having been forced off my path a couple of times, I refuse to be bullied on the freeway. If there are too many cars behind the offending driver for me to wait & get in behind him/her, I'll signal, give them a few seconds, then slowly start to get over. They can move it or lose it. I know this is dangerous, but golly, go figure - they always manage to find it in their hearts to let me in. 
I run as many errands as possible at night. It's just too frustrating here in the daytime; there's an idiot in every lane. It's virtually impossible to escape them. At least at night, you can go around them. The Silicon Valley has, without a doubt, the most unaware, rude, reckless and in general, unskilled drivers in the country. Period.
-SKesselman
Sarah, I think - well, I am almost certain - that I was a much more aggressive driver when I was younger. Now? Not so aggressive anymore. Lost my nerve? I don't think so. It is just that nowadays when I try to remember what I was in such a hurry about years ago, I realize that most of the time I wasn't really in a hurry at all. But when I was younger any other driver's inconsiderate or rude action toward me was taken as a challenge; a gauntlet thrown toward me, so to speak.
What an ass I was! I'm sure that I acted quite recklessly and just plain stupid, putting myself and others at risk by driving "competitively" for no other reason than pure pseudo-macho bulls***.
Hopefully we all get away from that kind of goofiness in time.

Jim