A Question for Game Developers (also asked on Y!Answers)

Developers' Thoughts on Let's Play Videos (S.978)?
So this S.978 bill is causing a lot of fervor among people on the web, mostly in terms of Let's Play videos. For those of you who don't know, a Let's Play (LP) is a largely unedited recording and streaming of a complete playthrough of a videogame. They're not exactly reviews as, well, movie reviews don't show you the whole entire film (they don't need to) while the critic reads their review. Basically, they're free shows instead of free samples.
Yet, I've been having arguments with people insisting that these playthrough videos HELP the industry, as in LPs are more effective (if not equally) as marketing tools than demos or rentals (wherein you'd actually play the game yourself) or reviews (which at most show brief clips). Someone told me they could furnish reports showing how they increase sales, but I'd rather hear from the horse's mouth, so to speak.
My question is, have any developers talked about LPs? Have any of them openly and explicitly praised LPs as a superior means to generating interest and getting word about their games out there than normal advertising methods? Basically, find me a quote from (let's say for the sake of argument) Dennis Dyack or one of the Bioware founders saying anything along the lines of, "if it weren't for those Let's Plays, we'd never see the kinds of sales figures we do now."

For me, I just can't see how watching someone play an entire game without paying anything to developers is a more effective marketing tool than seeing brief clips in a review or renting or downloading a demo of the game itself. How long does your test drive have to be before you decide whether or not you want to buy the car?

ADDED QUALIFIER: Avatar is the highest grossing film of 2010 and also the most pirated. Correlation is not causation, and I'll maintain that as the fallacy of that kind of defense until I hear it from a developer. Also, as a minor announcement: as much as I'd rather not do this, I've disabled Anonymous comments from this weblog. Say what you mean, mean what you say, and stand by it. If you really take issue with this bill, and can prove that LPs are essential to the point that making their production and distribution a felony will cripple the industry, stand and be counted.

Something of an update: Notch's adding of a gameplay video clause to the TOS of Minecraft doesn't count. Why? Because Minecraft relies on user-generated content; it's more of a virtual building tool than a game. Similarly, I wonder where Sony stands on gameplay videos for user-created levels in Little Big Planet?