The act of de-friending someone on Facebook may have just become a bit more socially awkward. There’s now a Greasemonkey add-on (available here) that will check your network at scheduled intervals to see if anyone has removed you and alert you when it happens.
As Inside Facebook points out, Facebook doesn’t offer this type of functionality natively. Thus, without the script (or something similar), you’d have to manually check your network for deserters, which would be insanely tedious, especially if you have hundreds of friends.
In other words, what was once fairly easy to get away with (de-friending someone) could become a confrontation if your ex-friend happens to have this script, called Facebook Friends Checker, installed.
Here in the Netherlands it's quite popular to de-friending someone @Hyves. Why because several accounts having so much friends, strangers, spammer and maybe stalker ;)
I removed yesterday 50% of my "friends" from my StumbleUpon account, most removed accounts are inactive for more than 12 month. This is not called de-friending, but "clean-up". On social webbsites we need friends related to our online indentity (or content). I go for the quality and not for the quantity