Here are some videos:

One cyclist blows thru 4-way stop without even looking until they were already in intersection and did not slow down at all. The other cyclist slowed, but also did not fully stop. Ooops.
http://www.youtube.com/watch?v=RyEBKs5Kv9I

Cyclist making left turn against traffic does not stop:
http://www.youtube.com/watch?v=7t04RKmSbD0

Motorist does not stop at stop sign:
http://www.youtube.com/watch?v=NFybHeszGTo

(This is not a statistical sample and not intended to prove any point of view)

Al