I think that a gathering of the best and brightest should be able to come up with some method of feedback a little more detailed than a simple thumbs up, more options are always better in my opinion. As any facebook user can tell you, a thumbs up is simply not enough.
I believe TED talks should do away with the "thumbs up" system to something more quantitative. The "thumbs up" method has been over used on the Internet and I don't think it really displays the truth of how people view things. I think they would be far better off to implement something that is unique.
An alternative to the thumbs up system would be something of a Likert scale. However, most people who use the approval systems will feel very strongly about it one way or another and use the extremes of the scale. This equates back to the thumbs up system that is already in place. No need to change.
No, TED talks should not do away with the thumbs up system to use something more quantitative, because the thumbs up system is simple and it is easy to understand. With a quantitative system, people could mean 1000 different things. Good or bad also stops people from being indecisive. They have to choose.
I think the TED talks should keep using the thumbs up system that it is currently using to judge the material of a segment. I think there is nothing wrong with it and is a simple way to rate the shows. Some people may think it isn't that classy, but I think the system makes it a lot more appealing.