I've seen it mentioned here and there that one isn't supposed to ride it all the way around (that is, on the horizontal sections), but the reason escapes me. If you stay inside the cabin, what exactly can go wrong? (serious question) Getting stuck doesn't seem logical, why would the probability of the paternoster stopping increase when there is a (modest) load on the horizontal sections?
;).
More seriously though, I guess it's not that you can't, only that you shouldn't, because there's always a shorter route to your destination that doesn't involve looping.