I will be extremely curious to see if this turns out to be a model that works well, and if Google/YouTube and Twitter winds up doing the same thing, or (maybe even better?) Facebook+Google+Twitter cooperate to share a single board.

It seems like it would be a smart move -- as long as the board comes up with respectable policies, it could effectively immediately insulate the companies from a lot of criticism.

On the other hand, allowing/removing content is only one part of the equation. Prioritizing which content to show (and to which users) is arguably a far bigger issue (with serious democratic implications) that this board doesn't appear to touch. But it's such a can of worms, I also don't see how they could.