Potential employers and colleges are likely to cite studies like the one conducted and published by the Journal of Applied Social Psychology, which found a correlation between a person's Facebook page and their job performance (via PC Mag):
Researchers asked a college professor and a pair of students to review Facebook profiles of employed college students. Afterwards, they answered various personality questions about the subjects, such as how trustworthy they were or how well they get along with others. They browsed a total of 274 profiles for about five to 10 minutes each.
Six months later, the researchers got performance reviews from about a quarter of the subjects' employers. The results showed that Facebook profiles were overwhelmingly accurate at predicting success - much better than even standard personality tests.
But is this reason enough to allow potential employers or colleges access to what is meant to be private information? Facebook is pushing back and noting this act of password sharing violates their privacy and user agreement policy, but currently the issue seems to be in legal limbo. This seems yet another reason to be careful about what you share online, as our private lives are slowly merging into a more public one, with or without your consent.
Concerned? Lifehacker offers some good advice: What Do I Do When My Employer Wants to be Too Social?.