A friend of mine told me the other day that he was working on a viral marketing project at work. He was trying to spread the word about a site he just released.

Curious, I asked him what activities he considered viral marketing activities. He listed building a Facebook page, postings in web forums and "Twittering."

To me, this isn't viral marketing. It's simply old fashioned advertising through new channels.

Viral marketing, on the other hand, is when a customer tells a friend who tells two friends who each tell four friends who each tell eight friends.

It's a passive activity for the marketer; the marketer isn't "doing" viral marketing, he's simply watching it happen.

But I do believe you can enable it in two ways:

By creating a product or service that is so cool that people are inclined to spread the word.
By making it REALLY easy for your customers to spread the word.

Beyond that, viral marketing is mostly luck.