I did not know this, but last Friday was supposed to be a Facebook Defriend Day. This was a day when you were meant to clean up your list of friends, i.e. remove those who are no longer your friends or you feel have mistreated you in some way.So if you log into Facebook today and notice that half of your friends are missing you will no why. However, it could take some time tracking down which friends have left, especially if you have hundreds of them. The reason being that Facebook does not have an email facility in place which informs you when a friend leaves and nor would they, as Facebook does not want to advertise that somebody has left the service, after all it’s bad for publicity.AdChoices广告A solution does exist, though, and takes the shape of 3rd party plug-in’s. One such example is the aptly named Defriend Alert which is no doubt trying to cash in on the above. It was developed by Seattle based Nick Patrick who has previously worked on iPhone apps, Reminders and Alarm System.There is nothing more to note about Defriend Alert, other than that once you grant it access to your Facebook account it will monitor your friends list and send out an email alerting you when one of your friends has decided to ditch you.Read more at Defriend Alert Brett’s OpinionI can see this being useful for business users, after all if one of your key customers ditches you it would be interesting to find out the reasons why. But for personal use I cannot see the point and I have a mis-trust for any application(s) that wants to gain access to my account. Besides, I have had friends defriend me on Facebook in the past and then a week later come back on-board, so if an app is emailing you every time a friend leaves it could lead to the wrong conclusions and invoke a ton of spam in your inbox to boot.For hundreds of friends it may be more useful, but I know some people who have friends on their list that they can’t remember who they are anyway, so being alerted to the fact they have gone doesn’t really seem like such a problem.