I think the Rent-a-pet things are ridiculous and solely for personal monetary gain, but the idea of a few separate owners sharing a pet might not be so bad. It would depend on the entire circumstance. If it provided 2 or more loving homes where the dog (pet) got constant attention and pampering, I can't find anything wrong with it. I think dogs would be much more adaptable to this than a cat or other critter would be though.
Thoughts?