Here are some examples of successful virals on the internet, both meme's and actual ad campaigns.
Afro Ninja
The success of this video is on it's comedy value. Much like 'You've Been Framed' it is funny to see people have accidents and hurt themselves in a way that isn't serious.
Bear Fight
This is an ad for John West Salmon. Again, it uses comedy but in a much more over the top way and is obviously set up (as opposed to being 'home footage' like afro ninja) but the absurdity of the situation as well as the way it is performed makes it very funny.
Laptop Butt
This is another ad, but for a Sony laptop. The product is shown but barely mentioned. Instead the focus is on the action. It is a combination of impressive feats plus ridiculous comedy. Two very compelling viral combinations. It has nothing to do with the product, yet the video is very popular.
Numa Numa
Don't underestimate the entertainment value of watching a fat person on youtube lipsyncing to a pop song. This is one of the most successful virals of all time and has spawned many clones. It isn't trying to sell anything, just silly comedy.