I'm subscribed to one of those neat little services that reports back to me when people UNfollow me on twitter. Most of the recent un-followers are either spammers or people I couldn't care less about. Why did they follow me? I have no clue! When I get a "new follower" alert I check (1)the quality of their tweets (2)frequency of their tweets and (3)if they are 99% re-tweets, I'm done: would NEVER bother following them back!