Kevin Allocca: Why videos go viral | Video on TED.com
I'll do most of the work for you:
1. Encourage Participation - get people to contribute and allow them to feel involved
2. Engage Taste Makers - target high influence people, and get them to talk about your video
3. Employ Unexpectedness - gotta break those expectations and give them something they don't expect to see. You have to be different to stand out
4. The final reason is in the vid ...and it's definitely worth watching
P.S. - This guy gets paid to watch youtube videos all day... how awesome would that be!