I dunno, I don't think that's true. You can replace the search function of Yahoo with Google, but that was only one of a bunch of things Yahoo was doing. You can't fly Southwest Airlines to Tokyo, but you can on American.
As a matter of fact, Southwest Airlines limited service reach makes many of the things they tout possible. AA could never, for instance, operate with only one kind of airplane.
People love the underdog. You might think of big bad Paypal as being the weak target, but I don't think anyone else does.
