GFDL 1.3: Wikipedia's exit permit

If I contribute to a project under the GPL (without "or any later version" clause) such as the Linux kernel, that has hundreds or thousands of different contributors, I can be certain the project will remain under the GPL, simply because it would be practically impossible to relicense.

In contrast, if I contribute to a project where I have to give atleast the right to relicense to a single external entity, I have to completely trust that entity. Not only as it is today, but also any group of people that may in the future get control of that entity. This could in principle include a hostile group getting control of the entity as the result of winning a court-case or whatever. (you lose a case, are unable to pay the damages awarded, and as a result all your assets are sold to the highest bidder, which could mean ANYONE)

I'm not saying it's a very likely scenario, obviously it would depend on which particular foundation gets the control. What I'm saying is it's in a sense safer to have NOBODY be in control, because it means that there is no single target to attack.