Participant observation can alter your perspective because you're, in a sense, sharing an experience with the people you're observing; in the hopes that you gain a better understanding of whatever it is that you're researching. You gain rapport, and a hands on view of what the participant's society is like in better detail than say a survey. The disadvantages are that you are likely to become biased. If sociology is the study of how people are being shaped and influenced by a social force; and you're there sharing that social force you are to some degree losing your objectivity. The ethics is as subjective as this type of science is. Beatings and drive-by shootings are a reality of today's society. Someone's presence there won't always necessarily change the outcome. The point of Sociology is to get a better idea of how our society works and why it came to be so. If we don't have active participant observations, we might not get such a detailed description of what's going on in the lives of the every day people who encounter experiences like these often. It is imperative to our history that sociologists document these type of societal occurrences.