It makes you wonder what private data sources actually have of the facebook graph (Not including facebook). Does someone have the whole facebook social graph downloaded or a large portion?
At 500+ mil users with an average of 150 connections, you're looking at 500,000,000 * 150 / 2 = 3.75e10 edges. Assuming generously that each edge can be stored with a 4 byte unsigned int, you're looking at about 140 GB. I haven't seen any scrapes that even come CLOSE to that, an that's ignoring throttling and privacy controls.
Edit: more likely, you'd get the data as (id1, id2) pairs with 8 byte longs for each id. That's about 600 GB.
You can get names and Facebook IDs of user's friends for anyone who signs in with your app. I don't believe you can fetch their friends through the API, so the game companies should have access to only edges in which one person uses a game.
The only way possible to download the whole FB social graph is to get permission to do so from every FB user. People can scrape public info but the social graph allows access to a users friends, friends of friends, likes, comments, checkins an so forth.
Edit: more likely, you'd get the data as (id1, id2) pairs with 8 byte longs for each id. That's about 600 GB.