If you go to Portland, Oregon, everyone wants to talk about Voodoo Doughnut. They talk about the caffeinated doughnut. Or the chocolate-glazed chocolate doughnut rolled in Cocoa Puffs cereal. Or the voodoo-doll-shaped doughnut that bleeds raspberry filling when impaled with a pretzel pin. Oh, did we mention that a Voodoo founder will conduct your wedding--with doughnuts and coffee for 10--for $175?

Dunkin' Donuts customers leave with tasty doughnuts. Voodoo customers leave with tasty doughnuts and a conversation to have with their friends.

Conversation isn't everything; clearly you'd take Dunkin' Donuts' P&L over Voodoo's. But all businesses today crave the credibility, not to mention the free advertising, that comes from word of mouth. As such marketing matures into its own discipline, more companies are thinking about how to kick-start it. So why is it rare to find a business that is good at sparking these customer conversations?

The conundrum for companies is that good products or services aren't enough. Ritz-Carlton hotels are undeniably among the best in the world. And yet, if you've just returned from a stay at the Ritz, what conversation do you have with your friends? "The hotel was great--check-in was faster than usual, the rooms were nicer than usual, and the food was more delicious than usual." Hmm. Better just show vacation photos.

On the other hand, consider Doubletree Hotels. In the lodging spectrum, Doubletree is a "medium"--nicer than La Quinta but not as full service as Four Seasons. It should be hard to find something to say about a medium player. And yet there's a conversation everyone has about the Doubletree: When you check in, they give you delicious, fresh-baked chocolate-chip cookies. These conversations provide a concrete symbol of warmth and homey service. (We baked cookies for you!) Cost aside, Ritz-Carltons would likely outrank Doubletree hotels in every conceivable survey dimension. Except the one that creates conversation.

Call it the 105% Rule. From a word-of-mouth perspective, it's virtually impossible to discuss an experience that is 5% better than the norm on all dimensions. People don't talk like mystery shoppers, reporting diligently on each relevant feature. People talk about the exceptions, the unexpected, the highlights.

If there's any place that's hard to find exceptions, it's the beverage case of a supermarket or café. Your bottle can be a little taller or have a cool photo, but really, it's all the same. That's exactly why Innocent Drinks, a juice and smoothie maker based in London, has a talkable personality. Four years ago, Innocent launched a campaign called "Supergran," in which English grannies knit little woolly hats for its seasonal winter smoothies (so the bottles don't catch a cold).

And we're not talking a couple of grannies, either. Due to demand for the hats (and the smoothies), Innocent lined up enough grannies to knit 230,000 of them in 2006. Even better, it donated a portion of sales revenues-- 50 pence per hat-wearing smoothie, £115,000 ($225,000) total--to Age Concern, a charity dedicated to keeping older people warm in the winter. Never thought a bottle of juice could be a conversation piece?