Yes, I do think that a large reason TED is so successful is that people are so willing to produce these talks. That is kind of the whole point of it, that's why their tag line is "ideas worth spreading." I happen to find the TED talks very inspirational, so I'm glad they're being done.
A TED talk is a way for someone who knows something about a topic to get his or her voice heard by many people in person and especially on line. Since we have become such an opinionated, and yet unheard by the government, society, these talks are becoming increasingly more popular.
Yes, TED is so successful because people are so willing to produce these talks, because no organization can be successful without a great deal of interest from the people. Those involved in TED are positive people who are motivated to make the world a better place. People are very capable of doing good.
TED is not successful because people are so willing to produce these talks but because people enjoy listening to the information. The talks introduce ideas to the community that involve goodwill and prosperity and these are issues people like to hear about. It is a different form of information people are not used to hearing about these days, in a world where so much negativity is thrown out by the media.
There will always be people willing to gain fame and national attention to their ideas, so its hard to say that any given person is the most important part of this. TED is successful because each video has a clear, definitive point that don't make people think or analyze too much.