Facebook has been through several iterations. Through those, I think they have made a lot of great improvements. They've added more features for people to communicate and share with, added the ability for third parties to extend Facebook with custom apps, and allow for other web sites to share information within a user's feed. However, with one of their updates, giving the ability of custom apps, a new form of spam has come.
Users can request you to add an app to your Facebook profile. Now, this would normally not be a problem, but people seem to love requesting everyone they are friends with to install their favorite apps. Personally, I hate getting these notifications. I just want the basic functionality out of Facebook: communicate with friends, share some photos, links, and other pieces from around the web, and that's about it.
Facebook has finally added the ability to block an app (as well as ignore a user's requests completely):
Thank you, Facebook!