Well, for one thing, this becomes a bigger and bigger problem: http://www.xkcd.com/792/ http://www.xkcd.com/792/ Yes, it's a ridiculous example, but the vast m

Well, for one thing, this becomes a bigger and bigger problem: http://www.xkcd.com/792/ http://www.xkcd.com/792/ Yes, it's a ridiculous example, but the vast majority of end users keep the same username and password for all of their online services. Obtain one U/P pair and you could conceivably access their identity anywhere. A centralized, specialized authentication provider could maintain multiple levels of authentication depending on what the service demanded. Perhaps your favorite news aggregator only required that you be authenticated with a username and password, but your bank could be using the same authentication service and demand a physical token or one-time password to continue to the service. The idea is to maintain the convenience we already demand and practice in a manner which is orders of magnitude more secure.