Interesting. Where I come from, some people say you can go up to 10 or 20 km/h higher than the prescribed 100km/h if the road conditions allow it, since it's the way most cars drive anyway. Now I live in Germany, and the fact that speed limits are not everywhere makes it easier to respect them when they come because a lot of the time, you expect that they are there for a valid reason. Also, if you just go with the flow, and the people in front of you get flashed, then you know about tickets and you can be smart and slow down.
I heard that some road enthusiasts and bikers in the States protested speed tickets in court because they argued that they were clearly just a money making tool, as there was no way that the speed limit could be justified to be X on a straight highway as even from x+20 it would still be perfectly safe and fluid etc. I've not heard much about them in the last few years though.