Covert participant observation raises serious ethical (moral) issues for researchers. These often conflict with the practical advantage it brings of observing natural behaviour
Researchers should obtain the informed consent of subjects, and reveal the purpose of the study and the uses to which the findings will be put. With covert observation, this cannot normally be done, at least until the research is completed
What people say they do when asked in a questionnaire, and what they actually do in real life, are not always the same thing. Participant observation can obtain rich qualitative data that provides a picture of how people really live
Allows the researcher to enter the situation with a relatively open mind, and to change direction to follow up new explanations as they are encountered. Theories are grounded in real experience
Can be the only viable method for studying certain groups, particularly those that are disreputable and suspicious of outsiders. Enables the sociologist to build rapport and gain trust
Some groups may not wish to be studied and can make access difficult, so participant observation often focuses on widely powerless groups who are less able to resist being studied
Covert participant observation is more likely than overt to be stressful and demanding for the researcher, due to the need to maintain their cover identity
Participant observation studies usually have very small, haphazardly selected samples, which provides a poor basis for making generalizations to the wider population
Participant observation is unlikely to produce reliable data, as so much depends on the personal skills and characteristics of the lone researcher, making replication by other researchers difficult
Participant observation studies may lack objectivity, as the researcher's own categories and ideas may be imposed on the data, and their sympathies may lead to a biased presentation of the group's viewpoint