Nike got it right where HTC failed.
The story is that the directors of the new ad for Fuelband fitness tracker decided to toss the script and just blow the budget travelling and make an ad out of the footage they got. I say 'the story goes' because I'm suspect that there may have been some degree of planning which is clearly not as cool as spontaneity. It makes a good story in any case, and a fun advert. You can view them both here:

http://www.fastcocreate.com/1680524/how-director-casey-neistat-went-rogue-with-nikes-new-ad

And the ad did indeed go viral, with 790k hits in less than a day.

A little while ago there was some discussion here about the shortcomings of the HTC ad (http://www.youtube.com/watch?v=HpCs92msJBs&feature=relmfu)which consisted of a shaky camera and some young 'uns doing fancy footwork over a conspicuously branded bus.

The reason why the Nike ad succeeds and the HTC ad sucks is that the HTC looks so painfully contrived. It probably did have a healthy budged, but someone got the wrong end of the stick, and thought that in order to go viral you had to make something that (looks) low budget. Inauthenticity is such a passion killer, I could've told them that.

On the other hand, Casey Neistat, the director of the Nike ad made no attempt to produce something that looked 'spontaneous' and 'street', he just lived the dream with a big fat wad of cash, and it does look real, and not over produced.

Neistat said that Nike had no involvement with the production, which is very rare. But perhaps that is the lesson to be learned; keep the budget and give free rein to your creative talent.