TED, I think, serves as a modern version of high-brow oration as the middle letter suggests: Entertainment. It's a double-ended marketplace platform of content providers (speakers) and content consumers (paid attendees and non-paid viewers). Since the cost is high to paid attendees, the content must be as good and fresh as humanly possible. From what I've seen as a non-paid viewer, I think TED accomplishes this reasonably well. It seems hard to have perfect criterion to choose whom to select and whom to not, when there is an abundance of interesting of voices, but unselected folks can always speak and publish on other platforms.

(Forward thinking can be controversial, but in order to not offend audiences and prevent attracting the wrong elements, it seems customary that such topics are passed on because the forum (e.g., intended audience/speaker experience) is inappropriate, although the topic may be vital, insightful and have a legitimate fora elsewhere. (Blasphemy, politics, etc.))