Well, that's basically the whole discussion. When we're able to shoot at ISO 6400- which is close to science fiction if you ask a photog. from the 70s - do we really need to have zoom lenses that are f2.8 or faster? I mean, the fast primes will hold their ground, i'm sure - superior IQ and such. But a 16-35 f2.8? 70-200 2.8? Who needs the weight and the size when you can just bump the ISO up a notch, or two, or all the way to 25000? Is "the chip" pulling the carpet from underneath the quest for the fastest lens? Are the photo companies shooting themselves in the leg?