Useful tool. Some advice: It seems the order of user is random, I hope there're some better algorithms to present the potential users I may want to kill. The activities of user, times of one user have been killed may count.
The criteria I look at when I do one of my periodic follower purges:
* Do I know them personally?
* Do I follow them back?
* Have they tweeted recently?
* Are their tweets content-laden or link spam?
* (Where you can add value: Do other people unfollow this person frequently?)
2) We actually do show if they follow you back, but I guess we need to make it more clear.
3) We also have a recent tweets/day as well as recent tweets. Again I guess we need to figure out how to emphasize this better.
4) This is actually good, how would you go about doing this?
5) Very smart idea, we will start tracking this in our DB. I think.
my 0.02