Just found the facebook, needs to be killed too.
2 Answers
Don't kill
Although questions about facebook itself are off topic, applications connecting with facebook are on topic, as long as they are not mobile applications.
I am thinking about facebook integration for chat clients, like pidgin and other software that interacts with facebook. Also there are browser plugins for facebook, like social fixer which might be on topic here, too.
If questions about facebook are off topic, but apps that connect to facebook are on topic, why not change the tag to facebook-related-app? That makes the tag more obvious, and finding related questions easier wouldn't it?