[justanotherbody]

It seems to me a lot of this starts with "I have a general idea, and I want to get it off the ground ASAP" and transitions to "I have a focused idea, and can now revise the project accordingly"

I see nothing wrong with that, as long as everyone involved recognizes the cost of rewriting/replacing large chunks later. If you're on a super tight schedule and don't want to write anything but JS, and you can afford to make revisions later (assuming the thing even catches on!) it strikes as pragmatic.

[nakkiel]

I think you nailed it. Different solution are valid at different times.

Also in many cases, a website rewrite is really nothing complicated.