I built this site as a way to track which friends on Facebook have chosen to unfriend me and which I've unfriended. Facebook does not seem to provide a record of these friendship transactions. They do, however, give you the ability to grant 3rd-party applications, like this one, access to bits of information about yourself - including your friend list.
With this list of names, I created a way to make back-ups of your friend list manually. This simple app gives you the ability to compare these back-ups for differences: additions and unfriendships.
When you click the Login with Facebook link, you'll be presented with a login dialog to Facebook, if you're not already logged in. After logging in you'll get a request for permission dialog. This confirmation is your way of allowing stillmyfriend to see your name, unique user id and list of friends.
Once logged in, you'll be able to make new 'back-ups' and compare them with previous ones. Stillmyfriend will only work at your request.
You are welcome to use this tool as well. Please read my about page if you have concerns about privacy.
Feel free to leave feedback here.