It's easy to implement, removes friction if you're developing a social app. However, you become reliant on facebook, search around and you'll find stories about

It's easy to implement, removes friction if you're developing a social app. However, you become reliant on facebook, search around and you'll find stories about developers having apps banned, etc. Also, if your app is not social, and there is no clear reason to integrate with facebook, users may be hesitant to use it.