All to often, people start using it as justification for income disparity, wealth disparity, minority crime rates and sometimes differences in economic development between different countries. Racism and classism aren't too far behind.

I'm reminded that it is no more noble to fool a person out of his money by outwitting him, than it is to bully him out of his money with superior strength. Being smarter isn't necessarily a moral justification for greater rewards.

Similarly, we rely on the economic system using prices as an information signalling mechanism; more valuable labour is priced up, and thus supply should follow. But if the valued labour is intelligent labour, and its supply is not easily increased, then there is less of a moral case for paying its suppliers more, for that attribute alone.