yeah, I see those on CL all the time and it's crossed my mind. That is a crazy amount of volume. I think most people interested in that kind of volume are into conicals and stuff, though.
Well, in any case, if you need to ferment a barrel and a half on the cheap, I don't see why not. Can you imagine the blowoff tube you'd need? It'd probably be 1" PVC feeding into a carboy with 2 gal of Starsan.