The wall is the most potent tool of Facebook research. It’s not necessarily the information content that’s important, but the date stamping feature that’s truly revealing. Remember the more time someone spends on facebook the less of a real life they’re having at the moment. So if that hot girl you added a week ago has been spending alot of time on FB lately, it can be a good time to practice those pick up techniques and have at it.
For girls, that might not necessarily be true. A correlation of increased facebook time for men usually indicates that he’s interested in someone, that could be you. If you get into it with a guy and he stays active on Facebook you might not be his main love interest.