I read an article this month in Car & Driver that Finland has passed a law in which traffic fines are now based on your annual income. So a person going 5 over may be fined $10 or $100,000 depending on whom they are. This bit the CEO of Nokia recently when he received a $12 MILLION fine for going 15 over.
Such a thing is, hopefully, unconstitutional in the United States. In the US, we're supposed to be equal under the law. Imagine the abuse a law like that could cause. Cities looking to increase revenue simply park officers in the wealthier parts of town. Wealthy people, effectively, would have less freedom than non-wealthy people since as a practical matter, most people speed from time to time but the wealthy would disproportionately have their speed limits enforced.
I understand the argument for such a law -- to the rich guy, a traffic fine is meaningless. A $100 fine is more of an annoyance to the millionaire due to having been stopped than the actual cost (and the increase in insurance is a bigger deal anyway). But all citizens are supposed to be equal in the eyes of the law. The rich pay far more in taxes but still have to drive on the same roads.
If speeding is really such a serious problem that people are flaunting the speed limits then lower the number of points someone can get before their license is taken away from them. Finland's laws, and others like it, seem like pretty transparent attempts for governments to justify squeezing more from its citizens.