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?
There would still be "IOUs" because gateways have to trust each other not to abuse the API. Typically this is done by each gateway holding a balance at each other gateway but you can see how that would quickly become prohibitive from both a cost and an administrative perspective.
Ya. I follow. So basically, Ripple provides a framework through which all these exchanges can achieve this.