I agree with Post #3.  It's good to find many different ways to teach our students, but sometimes too much of something is not a good thing.  We use slide shows, videos, guest speakers, TED, and documentaries to supplement our core curriculum.  This keeps the students stimulated and interested all the time, whereas if we used one particular medium they would get bored and we would lose their attention. 

As an individual I don't think I'd attend a TED conference, though they look very interesting.  That's not to say that they're not good; I just don't enjoy that kind of stuff.

I've used TED talks in my classrooms a couple different ways. The first way is more literal--as examples for public speaking. My sophomores analyzed the speech structure of "The amazing intelligence of crows: Joshua Klein" and also the physical and vocal inflections of "If I should have a daughter: Sarah Kay." These and many other TED talks accessible to a general audience show students a spectacular example of a professional speaker doing what they do!

I have also used TED talks conceptually. This year in my AP Literature class, I paired "The danger of a single story: Chimamanda Adichi" with our study of Wright's Native Son and "Dan Ariely asks, Are we in control of our own decisions?" along with Huxley's Brave New World. In those cases, we used our reactions and discoveries from the talks to spur topical discussions that we could connect to the reading.

It's one of my dreams to one day attend a TED conference! The talks are an amazing way to bring the ideas of great minds right into our classrooms, and surely belong in the classroom as something in the toolbox of teaching techniques. It is, as stolperia pointed out, imperative, though, that we take the  time to make relevant connections to the clips, though, if we expect students to truly learn from what they see and hear.  

Using any one kind of teaching tool or technique "all the time" is dangerous, because not all of your students are going to learn in the same ways you do and because anything becomes stale with too much use.

However, TED lectures are frequently very well done and very informative and enjoyable, which makes them memorable as well! By all means, use them when you have an example that is particularly well-suited to a topic being addressed in your curriculum. Don't show them simply because they are interesting - use them to support learning that needed to happen anyway.

I think TED talks can be a great assess to the classroom. They are usually relatively short and very visually appealing. Some lectures are even given by popular celebrities or TV personalities instead of scientists. One of my favorite TED talks was given by Adam Savage from Mythbusters. I think this type of program grabs interest and draws students in. This type of visual aid or media presentation can really help students grasp difficult concepts.