I'd rather see TED team up with another discussion forum (like Quora) insted of creating their own walled garden of conversation. Offering a way to talk with TED speakers on an already popular service sounds a lot more sustainable.
From the recent developments we have been hearing from Quora, maybe it is TED that is trying to break down Quora's walled garden. I am impressed that TED went out on their own, just hope they try and keep it as open as possible.