It is very tempting for marketers to become all sweaty about the prospect of a message going viral, all that free awareness, when in the old days, it would take lots and lots of advertising, costing big dollars.
If only it was that easy, just make a funny video and load it up!
It is still a matter of deciding who you want to delight, executing, and then you have a chance that they will spread the word, but without the focus on the small group to whom the experience of whatever it is you are selling is compelling, it is unlikely anyone will make the effort to spread your word for you.
In the early stages, it is inevitably, “one at a time” marketing, and the web does not make it easier than it has always been, it is just a different tool.