Do viral videos work as a successful advertising platform? The answer to that is in the strategy. Since you can not really control your target audience the videos are best suited to broad scale product/company awareness (I would actually compare it to a super ball ad). Content has to be catchy, short and usually humorous and or unusual. Once launched there are several different techniques for spreading your content and giving it a jump start.
Check out the Viral Video Chart from Advertising Age: http://adage.com/digital/article?article_id=137365
Also, take a look at 100 Million Views Club – “The list is a diverse collection of older and newer campaigns, including music videos, movie trailers, user-generated spots, and clips from TV shows. What they have in common is a massive total audience.”