Fllwrs

It can post automatic messages to your wall about it's findings but these can be turned off easily. This spam seems to be the major objection but it's very useful in letting you know who unfollowed you, so worth it.
Don't like the spam, turn it off.
I'm going to keep using it.

There's absolutely no DMs going on, I don't know what that reviewer is talking about. You can also change your setting so there's no tweets about who followed/unfollowed you. (The one with the goo.gl url was a beta-testing thing.) Useful tool.

Good site!
You can turn off automatic messages

I honestly don't know why this site gets so many bad ratings…all it does is keep track of your Twitter follows and unfollows. Sure, it uses your data, but the app needs it to work. Duh.

This website has been a great way of telling who is unfollowing me on twitter. Rather than making a list and checking it twice to see who has unfollowed me, this service keeps track of your new followers, and people that have been unfollowing you. It is amazing how well this works. Whenever I lose a follower I shoot them a tweet asking them what I was doing wrong for them. Usually, you can gain that follower back. This is an amazing service, and I will use it until the end of my twitter days.

Good information on what the application was set up for. Very accurate