The problems outlined above are common in much of the material available. Here in southern California, I am within an hour or two drive of some of the 35 Cahuilla speakers left. I cannot make contact with Cherokee speakers, for example, as easily. Once my grandmother died, I didn't know any other Cherokee speakers personally. I just drove in from someplace thousands of miles away that you never heard of.
Travel presents a problem.
People are interested in themselves. We are not going to make startling discoveries in a ten-week class. Some people pointed out that there is disagreement over whether or not Haida is a Na-Dene language. For purposes of my class exercise, if it is not, that's okay. If Haida is not related, then our simple exercise will probably show no relation at all, unless there is a coincidental cognate or two.