The people with bad cycling ettiquette almost always tend to be on either 1) dept. store mtn. bike 2) beach cruiser or 3) old, totally unmaintained road bike, typically a Schwinn but could go any different way. Out of these three groups, the grand majority of people I see doing the things I see are on the dept. store mountain bike.

Believe it or not, bike choice can say a lot about a person: just as riding brakeless can either suggest an expert/veteran rider who doesn't think they need a front brake, or a hopeless fashionista who just likes the look, a department store mtn. bike can denote someone who doesn't necessarily care about cycling outside of the fact that they can get to a destination slightly faster than walking, and typically won't take the time to figure out basic things like the right locks and right ways to lock up a bike, the fact that lights are a necessity at night or the laws of the road, i.e. not riding on the sidewalk.

This is not an end-all generalization, but it is a decent rule that is typically compatible with reality. You could reverse this rule to our side of the fence and use it to denote that track bike street riders generally have tighter (not necessarily skin tight) fitting clothing or ride with messenger bags or messenger backpacks instead of racks, panniers, and baskets.