The unique value of ethnography is that it reveals not just what people say or how they think, but also provides a clear understanding of how experiences work, so that businesses can see what actions they need to take to support, improve and change those experiences. […]
Ethnography can explain behaviour in ways that more traditional research can not. It is based on the assumption that people have reasons for what they do, even if those reasons seem inexplicable to the casual observer. Good ethnographic research will uncover the basis of behaviour of all key parties and throw into sharp relief the ways in which they might be misaligned.
Moreover, ethnographic tools are capable of producing far deeper description of behaviour, looking at multiple levels of resolution.
(via Usability News)