I recommend starting with the prescribed norms via the sites themselves, i.e., Terms of Use, etc. Then I’d research norms via popular techie online zines such as TechCrunch N Slashdot. After that I’d compare the terms and norms with usage via an ethnographic study using a strategic or random sample and inquiring of people’s usage (archival research) or perception (interview/survey) in the sample agrees, disagrees, or informs the prescribed norms elsewhere.