I always tell people: if you knew you wouldn't get a ticket in a car for running a red light safely, you would do it. As soon as the police start ticketing for running red lights and stop signs on a bike, I'll stop.
I ride in Philadelphia and I try to be somewhat considerate to drivers. I slow down for every stoplight and stop sign, but if nobody's coming, I'm going to go through it, because I'm not going to get in trouble.
The cases when the light is red and I, as a driver, can guarantee that I can run it _safely_ are very rare.
They are even rarer as a cyclist (takes me longer to clear the intersection).
The number of times that I have seen cyclists run red light safely (both for themselves and others in that intersection at the time) is precisely zero.
I've seen several hundred instances of cyclists running through intersections at this point.
The only good thing here from my point of view is that once I got out of big cities both cars and cyclists got a heck of a lot more courteous and law-abiding, so the number of people I have to deal with who're just completely ignoring the rules of the road, blocking intersections, etc is much lower. Good incentive to not live in a city again...
I ride in Philadelphia and I try to be somewhat considerate to drivers. I slow down for every stoplight and stop sign, but if nobody's coming, I'm going to go through it, because I'm not going to get in trouble.