Log in facebook in parse allows for read permissions. This doesn’t require to launch facebook app. Simple popup allows this. Instead it does everything in the background. We can pull fb user’s id, name and what not with such approach (within their permission). We can then link this to PFuser object in our User table. Parse allows devellopers to store and link uploaded photos by users on Parse. This opens up freedom to create applications to have linked users (by facebook) on Parse. One scenario:
User A logs in with facebook on app X. App X grabs all of his fb friend list and save it to Parse. Then, his friend user B logs in with facebook using app X. This gives us possibility to send a notification to the user A saying, your friend just joined the app. Birthdays: Login with facebook, your friends birthday and get automatic notification to your phone.