Create a three minutes version for each TED talk
I find it much easier to hook people up to TED if they have the option to watch a short talk first which will raise their interest to find out more and then they'll watch the average 20 minutes one.
A second argument is that we are all so busy and have so many things on our plates and there are not enough hours in a day. It's not a lack of interest that I am concerned about, but rather the trade off one needs to make to put aside 20 minutes which they usually don't have for something they don't know if they would like or not. How do you choose what talk to watch when there are five you may be interested in and you don't have more then half hour to do it?