I already have to worry about counterfeit electronics when ordering from Amazon. I’m not sure I’d trust them with prescriptions.
I expect pharmacies to double check everything they buy, and I somehow doubt Amazon will be able to ensure safety when the package is handled by 10 different people. If they develop some kind of (digital?) package seal, I might change my mind. Or every pill container has an RFID chip and is verifiable with the supplier‘s public certificate.