Usability (in the sense of a product not frustrating the user's intentions) will always be key to getting good word-of-mouth advertising. Friends don't tell their friends to buy frustrating products or services. When I first started using Google for Web searching, way back before Google's IPO, I told all my friends about it, because it got me better results than the other search engines of the time.<p>After edit: And the reason I knew about Google way back then is that I checked my server logs for my personal website, and noticed a new search engine spider coming by to visit. As I began using Google, I discovered its usability, and soon began telling everyone I knew, tech-oriented or not, about it. That's viral marketing at its best.