These man on the street stupidity bits are a staple of late night comedy, but for every stupid person, there could be 50 people who aren't stupid, and immediately get the joke. You just don't see the latter group. There's probably also a third, even smarter group, who understand that if they play along, they might end up on tv.
There's also groups of "stupid" people who believe the moon landing was a hoax or our education over here should help the Iraq. So what? Is the existence of uninformed people really breaking news?
