Unless you regularly monitor the friend count on your profile, you have no way of knowing when someone hits that “Unfriend” button. Enter Who Deleted Me, a Google Chrome and Firefox extension that checks your profile so you don’t have to. When you login with your Facebook account, the program saves your current friends list, then it rechecks the list whenever you click on the app and lets you know if there are any changes, i.e. when someone unfriends you. It also makes a distinction between those people and friends who just deactivated their accounts.