The first time a walkman was made, the guys at Sony decided to make word-of-mouth the way to propogate the product AB INITIO (right from the beginning !!). A few ladies and guys were asked to plug it in the ear and start jogging in the morning. People around them suddenly discovered a way to engage themselves with music and also disengage with the noise and traffic of the surroundings.
The rest as they say is history. This way of launching can be though argued as quite product specific, it brought an altogether new perspective in the marketing circle. The belief till then was that, word-of-mouth is something that is EARNED over a period of time and cannot be CREATED on purpose. This also described the old approach: the product should be of great quality, the service follow-ups should be prompt enough and all this will eventually lead to favourable opinion about the product/company and this will snowball into word-of-mouth(WOM) resulting in a natural advantage to the company. But Sony displayed (unintentionally I suppose) that WOM can be created right from the beginning and can be used as a unique approach to launch products. Thus a company could create and drive the WOM than being just a passive observer of it. That the product should be competitive enough is something that will remain uncontested though.
Today when I see around, I do not find products or services that have been able to create such WOM ab initio. You have huge hoardings or big budget ads or some other promotions that are just used to have a big-bang launch to create a splash. How much of these turn into sensible WOM that will help the product to break into the market is really questionable. I am yet to notice a powerful WOM induced marketing since the launch of Sony Walkman. The one that came closest and in some ways even crossed the Sony's was Google.
Although internet penetration itself was low at that time, especially in developing countries, the "Search" has been one of the most popular human activity ever. Google encashed it and probably summarised the entire value of Internet. All it did was provide a small bar and say "search". WOM spread out saying you can find anything and everything on the Net and how: just GOOGLE for it.
Came across a product that relied on the WOM induced marketing? Just let me know.