I lived in Co for 7 years - just moved away a few months ago. When I lived there, I drove into town (lived 37mi out of town in the mtns) and went on road rides with friends in town. I have seen both sides of the coin, and agree with others here that a) there is heated conflict in Co between bikes and cars, b) some in cars forget that those riding bikes are humans - they seem to confuse them with targets or something, c) some bicyclists after being abused by those in cars a number of times are becoming aggressive and 'clogging' roads on purpose. I have seen my friends do it.

It seems to me this is a classic example of a lack of communication. If we could all somehow sit down together and explain that it's just not safe to zip past a cyclist in a small passing zone (thus explaining the finger gestures in the general direction of said motorist), and that it's not polite to hold up traffic if it is possible to ride single file, perhaps we could all get along. Having said that, there will always be jerks on both sides. I see the situation getting worse, and short of some sort of outreach program (and let's face it, those rarely work), we cyclists will have to set an example by being overly polite, and when we drive, we can set an example by giving bicycles plenty of space and passing only when it is safe. Perhaps a letter writing campaign to local news papers?