Actually, there are 4 PhD programs in the U.S. in folklore, and many more master's. For the PhD programs, one's in California, one's in Texas, one's in Pennsylvania, and one's in Indiana. I've actually been thinking about going on to one of these programs. Given my interest in children's literature and folk and fairy tales, it might be a good career move, as there are few children's critics with formal folklore training.
But I don't know if you'd want to major in it as an undergrad. I'd think you'd want more of a broad education, and then narrow down as you go to higher degrees. But maybe that's my own personal bias, as my undergrad is in marriage, family, and human development, and my master's will be in children's literature. And to get my MFHD degree--well, not as part of the degree, but along the road--I took classes in animal science, agriculture, biology, family history, editing, art history, and photography. So I feel like I have a pretty broad background academically, none of which involves folklore or even English literature beyond one children's literature survey class.
Wait, no--I did take two writing classes my last semester. Okay, looking back on those two classes and looking at my purely literary masters, I agree with EUOL on the English thing. Writers do need writer's craft classes. I think that's the thinking behind MFA programs in writing, though--you get a background in whatever you want as an undergrad, then do a 1 1/2 to 2 year program that teaches you the craft of writing (and MFA is a terminal degree). My roommate has a degree in technical writing from her undergrad at Weber State, so some schools do offer some specialization.