Letterman just sounded dumb. Almost as if he was trying to make Formula 1 sound boring by making Seb explain DRS and KERS to people who have no interest in hearing things like that, and by complaining too much about F1 not being in Indy anymore and not being part of "the greatest spectacle in sport". The jab at Germany was awkward as well, and Letterman cut him off so many times. Seb had to force in his story about airport security at the end.
Check out his Top Gear interview, night and day difference.
http://www.topgear.com/uk/videos/seb...s-17-episode-3