Here's something related to my earlier Value of Choices post:
Highly trustworthy individuals think others are like them and tend to form beliefs that are too optimistic, causing them to assume too much social risk, to be cheated more often and ultimately perform less well than those who happen to have a trustworthiness level close to the mean of the population. On the other hand, the low-trustworthiness types form beliefs that are too conservative and thereby avoid being cheated, but give up profitable opportunities too often and, consequently, underperform. Our [empirical] estimates imply that the cost of either excessive or too little trust is comparable to the income lost by foregoing college. "
So having a realistic attitude about how much you should trust people means just as much to your wallet as going to college. Parents take note.