I've always be kinda sceptical about viral marketing. The reason being that it's always been much too dependant on a cool or freaky idea. If it was nog sexy, funny, controversial or voyeuristic, nobody would send it on to friends. And the people that would send it mostly fitted in the target groups "advertising professionals" or "people with an internet connection at work and no boss looking over their shoulder". Not really the kind of targetting everybody was dreaming about when the internet was discovered by advertisers.

But the world is changing (of course). The online crowd is growing so our target group expands in all directions. YouTube and Google Video let us forward links to online movies without congesting the mailservers. And broadband overcapacity lets us play freely with all kinds of interactive viral applications.

So what's happening now ...
"Viral" has simply become another way of distributing advertising. It can be video, which offers new challanges to TV-spot creators: no rules, no limitations. Or it can be an interactive application, a challange for interactive marketeers. But in any case, the consumer is the judge. If it's uninterresting, not compelling and not targeted at a target group with which I feel connected, it won't work.
Surprise, surprise: bringing a relevant message in an compelling way to the correct target group is what communcation has always been about.

In fact, good viral marketing comes down to simply good advertising. So we can stop making up lists of reasons WHETHER to use viral marketing, but work on a vision about WHEN to use this channel. This is my first attempt:

1. Objective: It works for branding, more then for selling or activating.

2. Target group: If your target group consists of (a) clearly defined community(ies), which you can reach in some way.

3. Timing: Being in a hurry doesn't work, there is no guarantee when the virus wil spread.

Feel free to add your ideas ...

To close this post, here is a great example of something that works:
Wanna work in advertising
1. It makes me feel this brand has something to offer me.
2. Me = an advertising professional = part of a community that communicates a lot amoung each other.