There is a great article on scaling web apps on Ars Technica, What Second Life can teach all companies about scaling web apps, which is about.. well, exactly that the title says.
From this passaage:
... but herein lies a trap for smaller ones: the belief that you can "do it right the first time." (Or, in the young-but-growing scenario, "do it right the second time.") This unlikely to be true in the real world, so successful scaling depends on adapting your technology as the system grows.
Regarding this, I said "You always throw the first one away"
My collegue Ross improved upon this with:
I'd say you throw the first (n-1) away since you're never really "done"
There is a great mathematical induction or recursion joke in here. This is left as an exercise to the reader.