Everyone's talking about viral marketing (Obviously it works...if everyone's talking about it!).

Just when you think it's old news, some ingenious marketer comes up with a new way to reinvigorate this tried-and-true business concept, traditionally known as referral marketing. Referral marketing is the art of getting people, who may not even be your customers, to refer your product or service to other people, typically their friends or acquaintances. Viral marketing, simply put, is referral marketing over the Internet.

In the first of this three-part series running for three consecutive weeks, I'll define viral marketing and tell you why you should consider using it. In ensuing weeks, I'll tell you how to measure the “viralocity” of a viral marketing campaign, and give you a list of 13 best practices for successful viral email marketing.

Viral Marketing Defined

“Viral marketing” was originally penned in a newsletter by venture capitalist Steve Jurvetson, who defined it as “network-enhanced word of mouth.”

While the word “viral” may have negative connotations (think “the flu” and “corrupted hard drive”), the concept is a positive one. Marketers have long believed that those who hear about a product or service from a friend are more likely to buy, and buy more quickly and easily. In fact, many articles on viral marketing make reference to a classic ‘70s Faberge TV commercial featuring sudsy-headed women telling “two friends.” And then, “they told two friends, and so on and so on and so on….”

While that commercial is probably the easiest way to illustrate the concept of viral marketing, it's not the most helpful example because: (1) most of us obviously can't afford to produce a TV commercial, and (2) now, with the Internet, and email in particular, you can tell more people about something faster than good-old-fashioned word of mouth.

Email: the Ideal Viral Marketing Tool

Email is an extremely fast and cost-effective viral marketing tool, especially for small business owners with little or no marketing budget. In today's wired world, an email sent to a contact list of only 20 people could potentially end up in the inboxes of hundreds, thousands, or even millions of “friends” around the globe.

When an email campaign travels beyond its original contact list, as recipients forward it to their friends, who forward it to their friends, and so on, we refer to it as “viral email marketing.”

Here are some campaign objectives that can be supported by viral email marketing:

• Increasing brand exposure: Sometimes all you want to do is be noticed, to start the lengthy process of getting your brand in front of as many people as possible. Encourage forwarding in your email and help your brand reach farther.
• Growing your opt-in list: Encourage your readers to forward your email. As long as it has a sign-up offer, you can encourage new signups—and even match those signups to the readers who did the original forwarding.
• Designing loyalty programs: If you knew who was successfully forwarding your emails the most, producing new subscribers or sales, wouldn't you want to thank that person and encourage them to keep it up? Viral email tracking systems can help you acknowledge or reward those special people who help you grow your business.
• Driving website traffic: If more people receive your email, more people will see and click on the link that takes them to your website—where they can be exposed to product information, cross-selling, sign-up offers, and so on. If you don't ask subscribers to forward an email, people often don't think to pass it along. Remind them in every email.
• Generating revenue, directly from the email: If your email contains a “buy now” button, you can directly correlate forwarding to revenues.
• Generating revenue from advertising: If people forward an email that contains an ad, more people obviously are exposed to it. You could be getting far more ad views and ad clicks than you expected, and these can translate directly into revenue. For example, in a recent viral email marketing campaign, the original email list generated 492 clicks, but after all the forwarding was done, there were 1,099 clicks—over twice as many clicks! Here's where the viral email tracking systems I mentioned earlier come into play.