Amazon.com has two-factor authentication!
I happened to be setting up a replacement phone and stumbled across this gem.
Use of an authenticator app or sms messages for authentication codes is now available.
With how much revenue flows through this website, securing customer accounts looks to at least be acknowledged. It goes a long way toward securing accounts that many of us use regularly. Though it might have been nice to be notified in red letters across the top of their page that two-factor authentication has arrived.
To find these settings start by going to your account page. Select Change Account Settings wherein you will find Advanced Security Settings followed by Preferred method for authentication code transmission.