Whilst I normaly agree with you Jacob, on your post above I think you are quite wrong. I am not saying that all, or even the majority of speed cameras are there primarily to maximise revenue, but from driving a lot of roads, there are some which seem to serve no other purpose.
All who drive should know what the speed limit on that particular stretch of road is, and should happily accept the consequences of being caught driving over that limit. If you didnt know what the speed limit is, then, again, it's your own fault. However, placing a camera at the base of a steepish dual carriageway gradient where the limit has dropped to 50, and it would be easy to over step slightly seems, to me, a revenue gaining exercise. Thats one specific Scottish example I can think of.
The debate as to whether the speed limit imposed is a reasonable one is different and moot.
If speed cameras are there purely to help prevent accidents, then road signs saying something to the effect of "There is a speed camera 100/200/300/etc metres away and the road speed limit is Xmph" would be much more effective at reducing speeds, but also much less effective at generating funds.
It all depends on whether speed cameras primary role is to catch people speeding, or help prevent the speeding in the first place.
Cheers.
Adam