Mav's right about most of it. Radar and Laser Detectors are useless by themselves, and most people on the road in this country take driving too lightly. But they are handy tools for situational awareness. Of course, I don't own one.
There are plenty of places in the country where local law enforcement and highway patrol uses speeding regulations to generate revenue. On the other side of town here, for example (iowa), we have a part of the city that's incorporated separately and has its own, very small police force). There's one road that goes through that area and connects two parts of the city (so city police on each side). That road has a 25mph speed limit, and is on a slight slope. 50% of the time I travel that road, I've been illuminated. Fortunately, I've been at or below 25mph.
Heck, I know of some towns where the cops are so notorious, people drive 5-10 mph under the limit just to be safe, only to get pulled over when their tires touch the yellow line.
And then there are groups like the flying tires of Ohio, who travel in wolfpacks, and have their favorite trap areas. Why come to think of it, when Moose drove out to Ohio a couple years ago, he got three speeding tickets, all in OH.
So, sure I believe there are plenty of smart cops out there who only use the radar/laser to confirm what's sufficiently obvious, but there are plenty of guys out there who find that parking and painting everything that goes by is just as effective.
What's ironic to me is that the situation for which a radar/laser detector would be most useful is also the one where speeding is the least dangerous: open freeways with no traffic. As long as there are other cars around, you can always spot a cop by the way every schmuck driver on the road panics and lays on the brakes.