‘There has been a fundamental shift in advertising in the last two or three years and viral marketing is changing very quickly too,’ says Colin Reeve of viral marketing company ViralFever.

An early example would be the approach that Microsoft took to its free hotmail accounts. On the bottom of every email was one line of text, advertising free email accounts. Around 150,000 people signed up to hotmail per day at its peak – that’s digital word of mouth.

If your viral catches on in the internet community, the speed at which it spreads can be phenomenal and the returns equally high. ‘It’s a great opportunity for growing companies to punch above their weight,’ says Matthew Mayes, creative director at marketing agency MRM Worldwide. ‘Campaigns can be very targeted and because of the recommendation or referral method of distributing the viral, they can have greater potency than other marketing techniques.’

Companies are now paying to have their viral videos hosted on video sites like YouTube and even using them to attempt to change the perception of a brand.

A clever disguise

‘People are often very negative about Microsoft as a business and don’t like the brand, so they chose to draw on that in a viral campaign called Stationery is Bad,’ explains Mayes.

The idea was that traditional stationery is intrinsically evil and will give you a hard time at work if you’re not careful. The videos released showed office workers involved in amusing stationery-related accidents and ended with the UR www.stationeryisbad.com – a landing site for Microsoft’s OneNote product. ‘The returns from that campaign came at a very low cost per product,’ beams Mayes.

Yet viral marketing doesn’t have to be based around amusing experiments or funny videos. The potential for distributing offers via email is also great if the approach is right and all you have to do is get the ball rolling.

Off-licence group Threshers ran an email coupon campaign before Christmas 2006, in which it appeared that a coupon intended for Threshers staff offering 40 per cent off champagne had been leaked onto the internet. The coupon spread via email and the weight of the ensuing traffic caused the Threshers website to crash.

Similar coupons have followed, such as the successful promotion from women’s lifestyle website Handbag.com. ‘We included a “send to a friend” link on the bottom of an email with a money-off voucher for the Wagamama restaurant and launched a competition to incentivise people to forward the email on,’ says Nicola Fitchett of Handbag.com.

‘The idea was to enter the most email addresses you could for the chance to win a designer handbag. The competition ran every day for a month and pictures of the bags were posted onto MySpace each day. In the end we had over a million entries to the competition and the promotion was more or less free to us.’

Powerful word of mouth indeed.