I am a biker and although I mostly bike trails I sometimes have to use main roads. I personally find bikers who fail to stop at stop signs to be annoying, rude, and dangerous. I understand why they do this - most people don't realize that a properly set bicycle seat leaves a rider practically standing on the pedals, so stopping means tipping the bike partially sideways to get a foot on the ground and then a pain in the ass move to get back up on the seat and start moving again. It is a pain in the ass but that said bikers should still stop when there are cars at the intersection - for their safety and the safety of those in cars. No one wants an accident but that is exactly what can happen when a car thinks a biker is stopping and begins to roll his/her vehicle and take off only to have the biker just keep going without a complete stop. I've seen nasty looks from drivers as bikers have done this to them. I don't blame them. Even when there is no one else at the stop bikers should still crawl to a near stop at the least and make sure the intersection is clear but I often see them just blow through. Not a good move.

I've seen the other stuff you point out too but this one in particular annoys the Hell out of me.