To summarize a prior discussion:

First, read: http://codahale.com/how-to-safely-store-a-password/

Next, note that rainbow tables don't enter into the Gawker break; Gawker used DES crypt(3) passwords, which can't readily be "rainbow tabled".

Finally, note that if you're going to advocate for a browser authentication change, there are cryptographically sound protocols that have been studied for over a decade that fit the bill far better than half-measures that do nothing but break "rainbow tables". A good one to start reading up on is SRP.