So I've read quite a bit about cob construction and even after this kind of research, I don't feel equipped to answer this question. What climates or locations make cob a good or bad idea?
One aspect along these lines with which I am comfortable is drainage. You want to be able to keep the 'feet' dry, so impossible drainage -- such as in a swamp, means that cob is a dumb choice.
I suspect that it can't be too hot. What about too cold? What else might I not even be imagining?