Tonight, while I should have been packing, watched a whole bunch of TED videos instead. One of the better ones was this talk by Kevin Allocca on 'Why videos go viral'. He should know his stuff too as the YouTube's Trends Manager, which allows him to "professionally watch YouTube videos".
In this entertaining and at times hilarious talk, Allocca shares his theories on why videos do get shared around so that a video of a cat watching a kitten watching Nyan Cat could be viewed millions of times. His main factors are the unexpectedness of the video (which end up being hilarious), a sense of participation (modern remix culture), and just dumb luck ('double rainbow' was uploaded months before Jimmy Kimmel tweeted it out).
Nothing ground breaking here, but worth a look if you're in the mood for a bit of a laugh.