What makes studying religion a challenge for scholars?

Religion is often a much more personal matter. In most subjects of scholarly interest, one can make an experiment or define the numbers and facts involved by simple observation. However, religion can mean many things, even to the same person; members of the same religion can believe completely different things, and still both be very "right". Thus, religion is not so easy to pin down or study. Because of the long histories involved, and the often sketchy and sometimes contradictory details, it is highly difficult to pick what you are studying in the first place, let alone actually study it.