Edit: I'm personally glad they went with the MIT license. Also, even if a fork takes place, the original code is still available.
jQuery changed the face of client side development, and its MIT license has encouraged significant and substantial corporate participation, but I have never even heard of a jquery fork. They actually have MS offering paid support for their library.
Rails changed the face of server side programming, and its MIT license has only increased corporate participation. Where is the rails fork?
Node.js changed the face of the app server landscape and is probably the latest big thing in web development. MIT license, where are the forks?
It is definitely a theoretical possibility, but it just doesn't seem to ever happen in this world. What does happen is you gain the ability to have companies throw money/manpower behind your project that they would otherwise have spent building a competing product that they could actually use.
I think this is a point many fail to consider. BSD and GPL are, in many ways, synergistic. Having libraries available in both is the best ecosystem for both devs and end-users, IMO.