There is no reason to go to all the effort of forking Wikipedia just to prove a point, and asking me to do so is absurd.

Let's ignore hosting. Let's ignore bandwidth. Let's ignore the amount of time it would take to duplicate that information. Let's ignore several "easy" (read: inconvenient to your argument that "you can just magically fork the datas!") issues I would encounter pursuing your suggested course of action.

From a practical standpoint, Wikipedia has become the place where normal people get information. It is the cache of human knowledge that is first hit when somebody wants to learn something new. I'm not talking about where you turn, or where I turn--I'm talking about Joe Blow. It seems to consistently be in the top few results for any search on a topic.

Ignore the encyclopedia bit. Ignore what it claims to be. Ignore even what it is. Pay attention to how it is used.

The de facto use of Wikipedia goes something like:

1. Person wants to know about concept X.

2. Person searches for X, probably gets a Wikipedia article.

3. Person reads article on X on Wikipedia.

So, it would seem that currently Wikipedia's use is to provide knowledge about X. The end user doesn't give two shits about the process that put that information there; or how reliable it is; or whether it is sourced primarily, secondarily, or made up entirely.

The end user just wants knowledge.

So, either one believes that Wikipedia has perfected the accomplishment of that mission (in which case I think you are obviously wrong), or one believes that Wikipedia has the capacity to be improved to meet that goal.

Are you going to take a hard line that Wikipedia is perfect in its accomplishment of its de facto use case? Are you going to argue that good is good enough?

EDIT: I'm not going to launch into how wasteful it would be to split up mindspace/SEOspace by creating another wiki. Suffice it to say that a mree policy change on Wikipedia could accomplish all this, while in the forking case you'd have all those "easy" problems to solve, plus promotion to get people (and lots of them!) involved, plus making sure people don't just default to Wikipedia anyways, etc.