How does viral marketing work?

It is quite amazing what you can do with social media and viral marketing now.
Thinking back only a few years the possibilities for online marketing seem very limited indeed.

I undertook a small experiment a few months ago during the thunderstorm over Berlin. I posted a photo of the storm onto Twitter and wrote about it on some community sites. I wanted to see how much attention this gets. Remember, this was just a picture of an event that occurs rather frequently. However, only seconds after posting about 40 people had viewed that pic. Another push came when a local newspaper retweeted my tweet and published the photo to their followers. I'm proud to announce that the picture got eventually 170 views! Plus, the local paper is now following me on Twitter.

This is a very good example of viral marketing. Exposure is generated by people sending on or repeating your message to their friends or contacts. You have probably heard of pyramide schemes before - the fraud case of Bernard Madoff is a rather infamous example - or I'm sure you have received chain letters by snail or email before. Viral marketing very much follows the same principle but in the positive sense of people wanting to inform their friends. If a message is not interesting enough to be forwarded on, they won't do so. There usually is no incentive or threat to retweet a message other than compelling content. Now imagine using that for business! Social Media network friends are usually trusted more. We don't think of Tweeters as institutions or corporations but individuals. This is a huge chance for businesses that use Web 2.0 and viral marketing effectively.

You need to have a story, though in order to initiate a conversation with people.
And if you don't have one, create it!