Facebook is kind of retarded, in that they give you a blanket "block all apps from my friends" option, but Windows Phone/Microsoft Live is one of those apps and you'll effectively prevent your phone from accessing facebook.
So, you have to individually block apps. What makes it retarded, is that to block an app, you have to approve the app first. Then you can block it. Then Remove it. This can ONLY be done with the web interface, not from your phone. If you go through the effort of blocking an app, it WILL NOT show up in your whats new on your phone anymore. It also must be the feeling a dog has when chasing his own tail.
I'm playing around with the idea of reporting all Apps as spam, to see if it will effectively block the app. Just don't want to inadverntently block a user that is a app-aholic.