If MtGox, BTC-e, CaVirtEx, etc. all started opening up all their data with one another, and allowing buy orders on one exchange to be fulfilled across this whole network of exchanges, would that not serve the function that ripple is now trying to fulfill? In that scenario, anyone could go to any of these exchanges to change their money to any currency supported by any of these exchanges... would we not then gain the same functionality as Ripple, but without IOUs or Ripples?