Interesting concept by Amazon with "Amazon Coins"
I'm guessing they are jumping on the BitCoin bandwagon with their own version; however, you can only use these on Amazon. Buy enough and you'll get up to 10% off, plus 10% off of your purchase. So I'm guessing that if you were going to buy something you may as well use these coins for a nice discount. The biggest drawback I see is that they don't do a 1 coin = $1 conversion, which ends up making it more complicated for those of us who can do math in our heads.