The "guy" in question isn't just anybody, it's Matti Leshem. Leshem is extremely well-connected in the Los Angeles production and marketing networks (I know of him tangentially from my television work), and his company, Protagonist, is Pepsi's primary strategy consultancy. I'm pretty sure TBWA\Chiat\Day is still Pepsi's marketer of record, but Protagonist drives the social push, broad strategy, and so on. They've worked with him over a decade so Leshem is basically a Pepsi man and the Mountain Dew angle of GAME_JAM makes a lot more sense in that context.

Based on what I've heard of him, Leshem turned a career making soap operas into one of those "high-energy brand power" sort of consultancies, the marketing equation solved to its limit that disgusts everyone when they think about "marketing." He and his wife represent a big Hollywood power couple -- she's high up at Warner Brothers and responsible for movies like Se7en and Benjamin Button, he's responsible for cultural triumphs like "USA Rock Paper Scissors League" (sponsored by Amp Energy, a PepsiCo brand, of course).

This article should explain a lot, from Variety in 2003: http://variety.com/2003/scene/news/branded-tv-bubbling-up-fr... -- I have no doubt in my mind that Matti Leshem showed up on set thinking "YouTube vehicle for Pepsi" and acted accordingly. Which should tell you a lot about Pepsi, honestly.