Right now when you log into an app with Facebook, the app developer collects a bunch of information about you. If you don't trust the app or you're afraid of spam, it may deter you from using the app or connecting it to your Facebook account.
With Facebook's new anonymous login, the user gets to control how much data--if any--gets shared with the app developer.
Here's how Zuckerberg explained it on stage:
“We know some people are scared of pressing this blue [Log In with Facebook] button. It’s some of the most common feedback we get on our platform…If you're using an app that you don't completely trust or you're worried might spam your friends, you're not going to give it a lot of permissions. Even if you don't want an app to know who you are yet, you still want a streamlined process for signing in...So last year, we separated out 'read' and 'publish' permissions. It helped people trust the blue button and sign into apps.”
Zuckerberg says the new anonymous login will allow people to “try apps without fear.”
Anonymous apps have been a hot recent trend in the startup world. Companies like Secret, Whisper and Yik Yak allow people to have no identity on their platforms and post whatever content or messages they want. Facebook's new login feature is a more secure way to keep your data on Facebook, without extending it to third party developers.
Here's what else Zuckerberg announced at F8.