At the risk of unleashing YAA (yet another acronym), I think it's time to start talking about CPB: cost-per-buzz.

Consider this: if you're a city dweller with an email account, you can expect a barrage of more than 2,000 unsolicited commercial emails a year sent by legitimate marketers and 4,000 spam emails every day. At the same time, you're exposed to 5,000 pieces of advertising every day. That's a lot of marketing noise. Now think about how many word-of-mouth referrals and recommendations you get? One a day? Two a week?

Word-of-mouth marketing is a rarified currency. And that, in part, is why it's so effective. According to a recent McKinsey & Company study, more than 90% of consumers regard word-of-mouth as the best source of information about products and services. Everyday brand evangelists work. Happy customers constitute a powerful army of word-of-mouth advocates. And the opt-in friends of those satisfied customers are, in the David Mamet vernacular, "the Glengarry leads."

So, how do you get there? How do you make online word-of-mouth programs happen and figure out if they're a viable part of your marketing mix?

First, get behind a good product or offer. Give potential brand advocates something to flak. A great product gets attention; so does a super-cool prize.

Second, make it easy. The most powerful part of a successful email campaign is the three-word link at the top and/or bottom of the page: "tell a friend." Every email should have one. The form should be simple, intuitive and honest, and the time required to fill it out should be miniscule compared to the reward to you and your friend.

Third, be transparent. Marketers need to be clear about benefits, prizes and privacy. Brand advocates need to be transparent about their relationship to the marketer--who they are, and why they think you should sign up, enter the contest, buy the gizmo.

Fourth, plan your next move. Have a strategy for sending a welcome email to new opt-ins, running contiguous promotions, eliciting feedback from new demographics and executing future word-of-mouth initiatives.

Finally, measure. While you cannot send emails to a recipient who receives a tell-a-friend message from your site, you can count how many such messages were sent. You can also ask those recipients to opt-in to future emails, and figure out the growth in the size of your opt-in database. You can then benchmark and compare to, say, your SEM universe or direct marketing campaign. One ROI equation might look like this: cost of email design and transmission + cost of incentive / number of new opt-ins = cost per buzz-generated subscriber (CPB, if my acronym sticks).

Put it all together, and hopefully you have an open-ended referral network that powers itself. You have a lot of people talking about your product or service, a new database of opt-ins, and increased sales or awareness. Best of all, you have a new marketing platform that is replicable and measurable, one that sings with a clarion voice above the undifferentiated marketing mulch.

This commentary is insightful. I recommend it to others.