Bike Safety

You are driving along and you spot a bicyclist ahead sharing the road. You're a biker too. So, just like the cars that you're watching, you keep an eye on the cyclist. But then, he does something unexpected—something that even seems dangerous to you.
But is it dangerous?
Why is it...that the cyclist in front of me at the red light is positioned in the center of the lane?
Why is it...that bicyclists ride near the traffic lane even though the shoulder is wide?
Why is it...that cyclists sometimes move into the center of the lane? If they are supposed to ride as hard to the right as is practicable, shouldn't they stay on the shoulder?
Why is it...that cyclists ride side by side a lot? I thought it was better if they drafted in single file?
Why is it...that cyclists got all upset back there?
Why is it...that when I come up on a cyclist at an intersection they get in the way?
Why is it... that cyclists don't use hand signals to tell me what they're going to do at intersections. Drivers have to signal, why don't cyclists? I never know what they are going to do and it's dangerous.
Why is it...that bicyclists fix their bikes right near the road where it's dangerous? Why don't they find a safe spot?
Why is it...that that cyclist is riding on the sidewalk? Isn't that illegal?
Why is it...that that cyclist I passed a ways back, just passed me and all the other cars waiting at the red light to get in front. Now I have to pass him again.