Who says that it's wrong to have a two-tiered hiring system: the standard "interview then hire" system (though done more rigorously---thus all the "how many golf balls in a schoolbus" questions); and the "let the market see how they do, then hire them at market value" startup acquisition approach. You can't have everyone at an organization as big as google go through the second process, so the first one fills out the engineering ranks.

See also: http://paulgraham.com/hiring.html