What's the difference between program and potential?
You CAN create a program that has viral potential. You can increase the viral potential of that program using various techniques that range from email pass-along to social tagging, SMS distribution, community based network monitoring, message boards, influencer payments, promotional product distribution cascading, MySpace friends, sign-ups for your family, your dog or your imaginary friend... any number of ideas that encourage adoption-pass-along-forwarding-communication peddling.

In fact, if you didn't pause at promotional product distribution cascading, you should have. I just made it up. It's my wonderful marketing speak for giving someone a tchotchke USB drive that has content on it that you are encouraged to share with others… ah, there's your spin.

It’s about trackability
It's easier for the agency to talk about the viral marketing program than explain all the nuances that often intellectually stump their clients. It’s difficult enough to explain to them what search engine marketing is. Viral marketing is a catch-all, a way to avoid talking about the details and about tracking.

And that's the key-- the difference between the internet's viral marketing and traditional WOM is trackability. That is what the technical proxy allows.

Viral and retro-viral-- be careful of awakening the dragon
When Universal Studios wanted to get the word out about "Serenity," a film based on the short-lived series "Firefly," the studio decided to tap into an ardent cult following that had sprung up around the cancelled series.

Using Affinitive's systems, they tapped into that devoted fanbase and encouraged the formation of regional groups and fan-support. When the movie was released on DVD, it not only became the No. 1 selling DVD on Amazon, but also propelled the original TV series DVDs to No. 2.
 
I rarely plug a company I have not used personally, but the success of "Serenity" and the Browncoat phenomenon is a very good example of how to best engage the consumer to encourage adoption of your message.
 
After all that success, how did Universal repay those evangelists? Well, it did what any media conglomerate does-- it started legal action against them,* demanding retro-active licensing fees and going after Cafe Press. The fans' response? Retroactively invoice Universal for their services.
 
Hmm...is this retro-viral marketing?

Consumer insights drive viral
Most programs relying on consumers to facilitate message distribution fail because clients want to control the message. Marketing programs that are often highlighted as viral successes were not designed as a "viral marketing program." They were simply astute marketing insights applied to reach the consumer, i.e., "There is a great core group of people who are still fanatical about 'Firefly,' even though we only ever aired a couple episodes. Maybe we could use them as evangelists for 'Serenity'?" The consumer was both receptive to the message and willing to communicate it to others. This is the power of WOM combined with the internet and the passion of those communicating.
 
When an agency that is not in the vertical space hits those nuggets of gold, it is often based on the pre-existing consumer passion for the product. If they were conscious of it that is great, but what I despise is when they re-spin it back to other clients saying, "we can do a viral marketing program like this for you!" It is your products -- and the consumers’ relationships with them -- that will dictate this more than the agency will.

Please, do us all a favor and stop saying you are going to create a viral marketing program, and just go create a good marketing program.