It sounds like it could be handy for international shipments? Normally it costs an arm and a leg to ship a heavy package overseas, but if a traveler has an extra check-in slot available, they could carry an extra 50 lb package for like $25. It normally costs like $300 to ship something that big overseas.
The liability and insurance issues would be pretty annoying to deal with, though.
The liability and insurance issues would be pretty annoying to deal with, though.