I'm following 97 people on Twitter now. The test for whether I follow/unfollow someone should be along the lines of: Do I actually feel better after reading this person's tweet? If it doesn't make me feel better, if it just feels like an obligation to absorb some information, or absorb a tone, or absorb an attitude, then it's probably not worth following the person.
Maybe there's a psychological way to describe that. Does seeing the person's tweet result in a positive valence or not?