If there is something in your news feed which you don't want to be there, you can click the down-pointing arrow. If it is created by an app, you can even hide all posts from that particular app.
A hide from all apps would be nice, but I think that would catch updates from cell phones and the like too.
PS: I understand a huge part of FB's appeal and page views is the stalker aspect, but just think of all the people that would love to be able to flag all farmvill traffic as spam or simply ignore all posts by apps.