not following back people.
Hope u didnt meant here black people.
Bad people? What is this?
How is it usefull? I mean people really follow people randomly? They need to know who they follow.
If that would be usefull that would already exist for every social website. Remove inactive friends, without profile picture etc.
I think he meant the follow back spree(If you follow me I will follow you) in twitter. It should be useful for some bounties which are asking for twitter audit links.