eMarketer reports that more than 65 million adults in the United States are already spreading the word about their favorite products and services. 27 million of them are doing it online. That number adds up to include about 17.5% of current U.S. Internet users. And it looks like those numbers aren't going anywhere but up...

If you look at eMarketer's chart, you'll see that word of mouth is expected to grow to include more than 20% of internet users (or roughly 34.4 million) by 2011. That makes sense as more and more users will become comfortable interacting with other users online.

It also drives home the idea that word of mouth marketing will be an essential way of reaching your potential customers and that you need to carefully consider how your online business will encourage word of mouth.