If only Facebook had control over how its data was used by third party developers. Oh wait...it does.
"Your phone knows where you are, because it’s there with you. And when you use social media to post photos and talk with friends about an event you’re at, that’s data that can be scraped and used… including by cops who want to figure out what you’re up to. But not so fast, Facebook now says: If you want to build an app for surveillance, you’re going to have to do it without their data."