As you might expect, ethnographic research is, in general a very time-consuming exercise - for a researcher to become fully-involved with a group may take months or in some cases years (and that's without thinking about how long it will take to write-up and publish the data collected).

During the period of involvement with the group the researcher has to be able to fund him / herself (food, clothing, shelter...) - another consideration to be taken into account when contemplating this type of research...