Your last point is exactly what makes these, and speeding camera, dangerous and even deadly. When these started going up in my state, I noticed a marked increase in rear-endings at the lights with these. My state also was the first to put the speed cameras on the freeway. Even though people routinely would do 90+ on that freeway, you rarely saw crashed.
After the speed camera's went up on the freeway, I personally witnessed 5 accidents directly caused by the camera. It didn't make people drive slower on that freeway, it just meant they would speed down the freeway, and SLAM on their brakes right before the camera, as to not get a ticket when passing the sensors. All it took was a driver not paying that much attention, and the driver in front of them changing speed by 20 MPH for no obvious reason, and BAM.
These things also have no judgement on whether your actions are safe, they just give you a ticket for doing anything over X. I don't know about you, but cruising under that limit to avoid a ticket, while every other car on the road is doing 10+ mph greater than you, is far more unsafe than the increase in speed. And it also works in the other direction: these things wont give someone a ticket for doing say 50 on the freeway, but if traffic is at a stop or slow crawl, you are being incredibly unsafe driving at those speeds, but the camera only sees you going under it's required limit.