My Commercial Transactions ProfPaces back and forth at the front of the classroom. Which is fine - I've dealt with pacers before. What I find distracting is the fact that he also chews his nails (or cuticles - I can't tell) while he's doing it.
So he'll pose a question, pick someone to answer, pace and chew, all the while muttering "Uh huh. Yeah. I think so!"
If he pulled out a cell phone and started talking, it would totally remind me of my brother-in-law. Or at least Mr. Q's impression of my BIL.