though it is a bit condescending to be waved through the intersection (no, i'm fine, thanks, i know how to ride on the streets), there are a lot of people who ride completely insane. in fact, many folks who ride predictably also ride erratically/dangerously/wickedfun sometimes.... so i guess that whatever communication between folks on the road is a good thing.
but yeah, i think people are generally a bit confused if the realize that somebody is pedaling and slowing down at the same time.