They are rather expensive for what you get, isn't it?I have to agree with Yellow Saddle & MacB, I have had a Rohloff equped Orange P7 MTB, the big advantage for MTB use is no mud clogging of the dérailleurs, and your never in the wrong gear at the bottom of a hill a quick twist of the shifter and the gear you want is there, the down side is you have to learn to ride with the extra weight on the back end, I went back to dérailleurs for MTB but I would have one for commuting or touring a very well engineered piece of kit although a bit expensive. can't see any advantage of belt drives.
Belt drive-----folder?Belt drives are ideal for pub bikes, folders, commuter bikes stored in your house/apartment, occasional use and rental bikes, very rainy regions, lazy cyclists, ladies wot lunch in posh frocks. Most of the interest and development has been by off-road sporty riders.
I've never seen any folder with a belt for the reasons you state, although they may exist.Belt drive-----folder?
That very much depends on how they fold, the B'Twin Tilt & Dahon type hinge around seatpost type fold that leaves the drivetrain in-situ ok, but a Brompton or Birdy up and under rear end fold that needs some semblance of chain tension when folded would be rather more difficult to accomplish with a belt.