At least over here, traffic lights fail and turn off on their own, no need for hackers :) . Now, fixing them (for example setting up a "green wave"... hmm that could be a more interesting use :)
For each given stop light, speed limit, and vehicle configuration, there is a rubicon that is crossed where it is impossible to stop before entering the intersection. Set up your camera and creep the yellow light time down past this limit and profits just start rolling in.
Exactly. There's uncountable number of stories easily google-able across the country where intersections with red light cameras magically coincidentally have their yellow light interval dropped by 1/4 to 1/3 vs intersections without red light cameras, to increase revenue.
You should also glance in your rear-view mirror to verify that the car behind you follows the same rule before you commit to stopping. Simple rules about traffic safety usually need a little tweaking IRL...
http://en.wikipedia.org/wiki/Green_wave