Ethnographic Study / Field Observation
http://jthom.best.vwh.net/usability/fieldobs.htm

Hom, James
VWH.net

Abstract:

Observing users in the field is often the best way to determine their usability requirements. Traditional usability testing, while providing a laboratory environment that makes data collection and recording easy, also removes the user and the product from the context of the workplace. Sometimes, it's best to see exactly how things are done in the real world.