I always thought this would be a good attack vector for hardware bitcoin wallets. You make a subtly backdoored version (for example, tamper with the RNG so it

I always thought this would be a good attack vector for hardware bitcoin wallets. You make a subtly backdoored version (for example, tamper with the RNG so it only has a few bits of entropy) and you either return it, or sign up as a third-party seller and ship it to Amazon yourself, to be commingled with existing legitimate inventory. Then a year or two later, because you know all but a few bits of the private key, you grab the money and run. No need to control who gets the backdoored devices, just ship enough that you luck into some rich buyers.