Jef Otte broke it down for us yesterday in "Denver Bike to Work Day 2011: Don't be a dickhead," a post that solicited this comment from Moodeous:
SO GLAD turn signals are number one. As a cyclist this is my #1 pet peeve. I know I'm not always in the right either, but if you would use your MFing signal we could avoid a whole lot of BS. So much so that I've considered custom making a patch for my bag proclaiming "I <3 Turn Signals", "Turn Signals are Sexy" or "Signal Bitches!". Thanks for this!
Thanks, Moodeous. And put us down for a patch if you ever make them.