Hint: if your app isn't working check if Facebook didn't unset your app namespace. If so, set it again and save changes. Probably it was possible to take over other developers app namespaces due to this bug.
The main benefit you mention is the biggest disadvantage of this solution as you may need to scale it as traffic grows. You can avoid it by using S3/GH Pages.
Bitcoin are "mined" by miners across the globe who run special software on their machines/mining rigs. Each time a block was mined before block #210 000 miner earned 50 bitcoins (+transaction fees). Now, it will got only 25 bitcoins. It's part of Bitcoin specification. More reading: https://en.bitcoin.it/wiki/Mining#Reward
