Okay, I have nothing really to add on this, but this blog entry by Brendan Eich, inventor of JavaScript, was simply so brilliant I had to point it out:
Forking is an extreme point in a continuum of options that exist with open source. The option to fork must exist as a feedback mechanism, but it need not be used in order for users to gain benefits not available with closed source and proprietary standards. Forking can be the right thing, or it can be a kind of mutually-assured-destruction option that keeps everyone acting in the interest of not forking.
Forking is not evil. The right to fork is a feature, not a bug. (And this makes Sun’s long-standing resistance to open-sourcing Java — recently overcome, happy happy joy joy — out of “fear of forking” seem especially short-sighted.)