Viral marketing is without question the most powerful and cost effective method for promoting your site online. Unfortunately it is also one of the least reliable. This is because in a viral mode, the recipient of your message is also the channel for distribution of the message. If your message does not inspire the recipient to pass it along to others, the campaign fails.

Like all things online, viral marketing is mostly about content. Your content has to hit the mark in an ever-changing social and technological context. While this is extremely challenging in itself, an effective campaign must also inspire some of the people who see it to not only pass it along, but to take the desired action. Having a million people read your message is a hollow achievement if nobody makes a purchase.

The success of a viral campaign is also dependent on the initial distribution of the message. As an example, if three out of every ten recipients will forward your message, then sending it to three people initially is likely to fail. Starting with 10,000 people is much more likely to get positive results.

The last factor to consider is overwhelming success. If your message takes off rapidly and has a very high referral rate, your site will be put under incredible load in no time. Unless you have prepared for this in advance, it is highly probable that your site will be unable to meet the demand. This can quickly smother an otherwise outstanding success, and leave prospects with a negative impression of your business.