[cperciva]

Not to derail your question, but my brother got a BA in philosophy, decided that he was really more interested in music, got a BMus, decided he was interested in the application of technology to music teaching, got an MA in "interdisciplinary" (music and computing), then decided machine learning was cool and decided to teach a machine learning system to play violin, and is now getting a PhD in "electrical engineering" (which is really CS in this case).

So in at least some cases, people get odd combinations of degrees more by accident than design.