The OnMedia event this week in New York included their Best of Broadband Advertising Awards for 2007. I've seen more than half of these videos featured here on MarCom Professional, but I've included my favourite of the bunch below. You can see all the winners here.
Produced by Omnicon's Cutwater (although not going to win a prize soon for accessibility of their own website) and made to look user-generated, the video went viral because, like anything and everything that "goes viral", it's interesting content. This time the interesting comes in the form of "how did they do that?", so you pass it on to ask that questions of your friends.
Combine this with some Google SEO on the phrase "Never hide" scrawled in the dust of the car at the end of the video to point you to Ray-Ban, and you have entertainment combined with self-congratulations that you worked it out :-)