I know that people had a fit and Ebay doesn't sell live animals anymore.
With Wal Mart, the rescues are alright, but not the pure breeds, because that gives people a good excuse to keep breeding, like a puppy mill.
Actually (being a former EBayer) - they had problems with the health of animals - and the safe transport of pets on airplanes. Many problems. And the obvious of course - you bid for a breed that is not a breed. Its hard enough to transport live plants.
And since EBay is supposedly open to the world wide marketpplace - you would get bidders from questionable sources - and you really can't fit the regs to transport live animals out of the country.