Google has a good Yubikey implementation (they allow multiple keys), Amazon and PayPal are 100% crap implementations. I had a website with probably 10K monthly

Google has a good Yubikey implementation (they allow multiple keys), Amazon and PayPal are 100% crap implementations. I had a website with probably 10K monthly active users go down for a week because I was travelling with a different Yubikey and AWS only allows 1 Yubikey to be registered. I've also had PayPal payments have to be delayed until I got back home because of the same reason, they only allow 1 Yubikey. Horrible quality products.