One sure use of these fake CCs is on Priceline.
I know for certain that it "works" there for bidding.
That is, you can't actually get a room, but you can use the fake identity/CC to name your own price, and lowball the fuck out of them until you get something you like. Keep repeating with different identities/CCs (in Chrome Incognito mode, so no cookies save) until you get a price you like.
Once your price gets accepted, it will try to charge the card and fail, and then it will tell you "there's a problem with your payment".
Then you just close it, sign in as yourself, and bid the identical price.
This will also help you find good prices to use for bidding:
http://www.betterbidding.com
None of this is illegal, because you're not actually charging anything to these cards, and the cards themselves are fake and not registered to anyone.