Sure, but wikipedia succeeds where forks like Wikinfo didn't (What's Wikinfo? Exactly.) for the same reason that betamax and Ebay's competitors failed: the more people use a particular format or site, the more useful that site becomes, the more people want to use it.
Why shouldn't Wikipedia have an exhaustive entry on the Heavy Metal Umlaut? It's not like it's taking up space that we can't spare; hard drives are cheap.
There might be a time when forks will work well, but that'll be several years from now, when the user base is much bigger and there are better sofware interfaces and visualizations to sort through the differences between the forks.
Ben Yates Wikipedia blog - http://wikip.blogspot.com