However, then Ripple came along. If it gains mass acceptance
Except Ripple can't be trusted because it is closed source, centrally controlled, and they lie about it on their home page.
I know about the controversy, but a) most people out there don't care, and b) the point I made doesn't have much to do with the current implementation at ripple.com, same would be true if we had a more decentralized one that builds upon Open Transactions + BitMessage or with Colored Coins or whatever. As soon as we have a network that allows to conveniently transfer promises or IOUs and that catches on, the cat is out of the bag, pandora's box is open once again and fractional reserve bitcoining will be made easy.