All marketers want word-of-mouth (WOM) and why wouldn’t they? It’s long been considered the best possible brand booster. But it’s always come with the assumption that because of the elusive and ephemeral nature of conversations, you can’t use it like any other media. But you can.

A recent report from the US by PQ Media found that by 2013 WOM as a media channel will be a $3 billion industry (roughly representing more than 10% of media budgets).

A conversation is the metric of the WOM industry, just as magazines have readers and TV has a TARP. One important difference between a conversation and other media channels is that someone is definitely listening and the conversation is likely to be very relevant to them. In other words you have active, rather than passive communication.

The obvious question is that if WOM can be bought as a media impression, does that make it inauthentic? It does seem wrong to consider buying a conversation. But I don’t mean the few shameful examples where brands have attempted to buy these conversations through paid recommendations or generated conversations without transparency.

Like any targeted communication, for WOM to work (and to keep working) the conversation needs to be based on something that someone genuinely likes and wants to tell other people about it. Of course, not everyone has an iPod to launch, but someone, somewhere is going to be enthusiastic about your brand. But if you have a dog of a product, then just forget about WOM marketing, it won’t work – all the new media in the world still can’t polish a turd.

And while I’m at it, any word of mouth model that involves incentives, points or cold-hard cash is misguided and ultimately ineffective because it is not genuine.

From our research across close to 100 campaigns at Soup we’re getting pretty good at predicting how many conversations an influencer will have about a product/service/idea we involve them in, with the average number of conversations being 14.8 within one month. This number increases by another 60 percent over the next two months, bringing the total up to 23.7 conversations over a three month period. In terms of media impressions this starts to significantly add up, especially when you factor in how many conversations those people then go on to have about the products or services (an average of six more each, in case you were wondering). Interestingly, this correlates with research in the US with word of mouth measurement experts Chat Threads showing the cross continent rules apply.

And marketers shouldn’t be afraid of customers saying negative things about their brands. If you run a WOM campaign, and there are negative comments in the mix, then it can give a marketer valuable insights into how the brand could potentially be improved and in fact it makes the other word of mouth believable that you haven’t tried to control the conversation. For example, research by www.bazaarvoice.com shows that user reviews that had some negative comments were overall more believable and influential in purchasing.

WOM is obviously effective, but you should always generate it without losing the authenticity which is the hallmark of any good WOM. The key is transparency. People need to be able to say exactly what they think about a product or service, and as soon as you bring money or incentives into the picture, you’ll fail before you’ve begun.