the perfect 'viral video' example I can think of. Free advertising for Nike. Kobe does something crazy and the whole internet tunes in, little do they realize, he is just advertising for his shoes.
Heres another great example. Purposely made viral. The Band OK GO likes to make amazing music videos that go viral. They embed them all over the place and get the internet buzzing about them.
another excellent example.. A teaser trailer for a movie called cloverfield. This was one of the best viral marketing campaigns I have seen. They release a trailer for a movie, trailer ends with a huge explosion and the statue of liberty head flying through the air and landing on the ground before the camera cuts..needless to say, but this had the internet buzzing for a couple months about what it could possibly be about.
