What a terrible word, viral. I have always felt this. Every single day, I get an e-mail from someone who does 'viral video' or wants help creating a 'viral campaign'. If any word has a negative connotation to social human interaction, it's the word virus. A virus, Latin for poison, is a particle that infects biological organisms (like humans for instance). In all likelihood, one day, someone will unleash a human-made virus and kill everyone. Then we won't have any words at all.
In the meantime, one great replacement is the word 'meme'. This is the word I prefer to describe the phenomenon of content or ideas that really strike a chord in people. The word 'meme' was first introduced in 1976 by evolutionary biologist Richard Dawkins in his book The Selfish Gene. The word refers to 'a replicator of cultural information' that one mind transmits in some form to another.
I first learned about the word in a collaboration at Parsons in 2002 with Eyebeam's Joana Peretti. Jonah became famous accidentally for his e-mail correspondence with Nike over their custom stitch offer (after Nike's refusal to stitch the words 'slave labor' into his shoes, Joana passed the funny emails on to a few friends who then forwarded it on, eventually reaching millions of people).
Memes propagate amazingly well through the digital world obviously because of the speed, reach and lack of resistance in place to carry them. We seem to be in a phase of community/bridge building with the web in general where memes are even more kinetic.
Online memetics is a fun study but the best usually come about naturally. . It's an easy discussion because the qualities behind the most far reaching memes tend to be easily understood. In the same vain, when people say a good liberal arts education contributes to a well rounded perspective on the world, I often say an understanding of online memetics contributes to a well rounded perspective on contemporary social consciousness. As clever representations of strong social sentiments it's often difficult to suppress the desire to share.
Viral is a strong word, a great metaphore that you feel in your gut. Meme? It's academic, intellectual, all in your head, no emotion. Memetic is even worse.
Viral stuff usually makes you see different, twisting your assumptions. Or sometimes it just makes you laugh. But a viral thing is usually unique, or even uniquely unique, each a mini cultural breakthrough. The sort of thing that used to happen a couple times a year back before WWW, and now happens a couple times a week. This has hugely accelerated cultural evolution. Toffler had no idea.