But what if I'm using it as a noun object, referred to in the singular? When I refer someone to a "website", I'm surely not sending them to the Web in general. But then again.. if we're going to be that way about it, shouldn't we be saying "World Wide Web site"? After all, in this context, the word "web" itself is a corruption. Should "web" be capitalized? If not, however are we going to know that it doesn't refer to spider webs, webs of deceit, or industrial webbing? Referring to it as a one-word term resolves these issues nicely.
New words have been created from combining words and word fragments for thousands of years. Seeing that the words "web" and "site" weren't typically used together until about ten years ago, I think the grammar nazi jury is still pretty much out to lunch on that one.
Personally, I think "website" will ultimately win out on my side of the Atlantic; we Yanks typically fall back on the colloquial. It wouldn't surprise me at all, though, if "web site" ended up being the preferred term in the U.K. and in other nations that hold to language usage conforming more to the Queen's English.