Hi, I work at Stellar. The FB auth is the first of several methods to receive stellars so we will add more methods soon.

Also, mining obviously has many benefits, but it's still limited to people who are highly technical and/or who have money to spend. We wanted to provide much broader access to digital currency, and so stellars will be given away for free at the click of a button.

To encourage transparency, anyone can see how many stellars have been given away here: https://www.stellar.org/stats/