This is a great question. There are many disadvantages and advantages to invasive research in social research. Let me name a few of them.
When a researcher is studying a society or an aspect of a society, he or she should try to observe without changing that society. Of course, this is not possible completely, but it should be a goal to the best of a person's ability. The reason for this is simple. If a researcher changes the object of study, then that researcher's study is not pristine. From this perspective, we can say that the more invasive a researcher is, the more that person may change that soceity. This is a disadvantage.
The advantage of invasive research is that the research can be done on a more thorough level. In other words, you can break through the superficialities. If this can be done without changing the culture, then this is the best option.
Thank you so very much!