About ten years ago, when Forrester was writing some of our early research on effective Web design, we noticed a pattern among leading companies. They told us they were finding it very helpful to use design personas - models of customers based on qualitative research into real customers, but presented as vivid stories about individuals (not segment descriptions). These tools enabled them to stay focused on the needs of their most important customers when designing online experiences.
Since then, design personas have become fairly mainstream design tools in North American companies, and increasingly common in Europe and Japan - not only for Web design, but across all channels. However, the quality of personas varies enormously from company to company. For example, I'm evaluating personas from UK interactive agencies at the moment and although some are clearly well researched, engaging, helpful to designers and believable, others seem to be mere stereotypes.