A number of strenghts have already been described under “When to use observations?”. We could add that:
- Observation has the advantage of capturing data in more natural circumstances84.
- The Hawthorne effect is an obvious drawback but once the initial stages of entering the field are past most professionals are too busy to maintain behaviour that is radically different from normal84
- It can be very difficult to get access to the setting
:An observer is often experienced as a threat, especially if the setting is not asking for the research to take place. Observation (and especially participant observation) might lead to knowledge of informal procedures or rules, which people do not want to be uncovered. Also the researcher can be experienced or perceived as a barrier for the normal daily routine in the setting10. In direct observation, the researcher does not participate in the setting, hence is known as a stranger and gets only access to the public or formal layer of the social reality. He does not become an insider and will miss inside information because he is too distant from the actors he is observing10. “Access, then, is not a straightforward process of speaking to the person in charge and obtaining the approval of the ethics committee. It usually involves considerable time and effort and a constant endeavour to strive for ‘cultural acceptability’ with the gatekeepers and participants in research sites” (p. 310)84.
- Once inside the setting there is the problem of avoiding “going native”: This means “becoming so immersed in the group culture that the research agenda is lost or that it becomes extremely difficult or emotionally draining to exit the field and conclude the data collection” (p. 183)20.
- Observational data, are more than interview data, subject to interpretation by the researcher. Observers have a great degree of freedom and autonomy regarding what they choose to observe and how they filter the information84.
- Observations are time-consuming and hard work at every possible hour of the day.
- An observer can get emotionally involved in what he observes, and by consequence lose his neutrality
- It is impossible to write down everything that is important while observing (and participating). The researcher must rely on his memory and have the discipline to write down and expand the field notes soon and as completely as possible54.
 The Hawthorne effect is the process where human subjects of an experiment change their behavior, simply because they are being studied http://www.experiment-resources.com/hawthorne-effect.html.