People slamming on brakes waaaay early, the instant the light turns yellow, afraid that they're going to get a ticket. When in actuality they and another car could have gone through OK. Also, redlight camera companies have been proven, with the local government's permission and blessing, to actually SHORTEN the length of time of a yellow light. Then it really makes the situation less safe, and all about the revenues for the government.
Then there's the video from an intersection in LA, watch as it turns from yellow to red:
YouTube - Los Angeles' Right-Turn Red Light Camera Trap
The blue car got a ticket. And the timing of the light was done on purpose to maximize revenue.