Sounds like we had really similar experiences. I wondered whether it wasn't nervous laughter, too . . . my ex-room mate laughs at movies when they make her uncomfortable, and a lot of people do that in general. And if it had just been a nervous titter or two, I would've said that's definitely it. But the fact that the laughter really was quite . . . hearty, and the fact that the reporter guy--and now you, too--experienced the exact same thing--just makes me wonder whether there's some other explanation I'm missing.