some people just get very stupid when they see a bike. They get this idea in their head that probably goes something like this (imaging Tarzan style voice and IQ that receeds to about 10 when behind the wheel)

bike - bike slow!
me fast - me very important!
bike bad - me good - must pass really fast and close to teach bike a lesson!
bike will learn to stay off road - road belong to cars!

It doesn't even occur to many of them that they are only rushing to the next red light..... It's really fun when someone does something extremely stupid and you can pass them by at the next light.... I don't normally filter up at lights, but sometimes I can't resist letting an @ss know that pretty much no matter what he does in city traffic I can get there just as fast as he can....

I also admit to taking some pleasure out of baiting some people to speed... there are several places that I can consistently do the speed limit and I try to see just how many people still feel the need to "teach me a lesson" about how slow bikes are...