Have you asked yourself this? Well you're in luck - ManageFlitter has the answer!
Click "Connect to Twitter" below to connect your account. We'll process data on your followers and within a few seconds you'll see the screen below - a list of all the people who have unfollowed you. If you feel like it, you can then select some people and unfollow them quickly by clicking the button on the right.
Apart from being the perfect answer to who unfollowed me, ManageFlitter is a world class Twitter management tool. ManageFlitter's feature focus on 5 key areas of Twitter; Unfollowing, Following, Searching, Twitter Analytics and Posting.
More detail about each of these can be found on the ManageFlitter Features page.
It's completely free to find out who has unfollowed you. ManageFlitter also has a premium version, ManageFlitter Pro which contains many more powerful features. While ManageFlitter is very usable in the free version, many agencies & individuals sign up to the Pro service for much faster growth of their Twitter account.