MFA is basically another key|password. If I am not careful with my secret key and password what difference does it make that there are two of them?

No, security is tough. The better security the less useful it is. NIST got this right. Do what you can, don't kill the user and implement security on the aaa side.

Have you ever messed with a friend by locking out their phone?

I was specifically addressing the DoS vulnerability of locking an organization out en masse by taking advantage of account lockout or timeout policy. A list of emails and a six line script could take a whole company offline.

MFA can be used to address that by requiring pre-auth before you can enter a password.

MFA is not a magic solution to all problems either. You can't expect me to give my phone number or real email address to every random site I login into.

You don't need to do that for HOTP/TOTP though.

1. Scan a QR code.

2. You now have a secret value that can generate a deterministic pseudorandom integer securely indefinitely.

Also, SMS-based MFA should be burned to the ground.

Scanning a QR code by hand is easy when you don't have the phone handy. (sarcasm)

Actual OTP should allow you to print out or write down a set of codes.

> Scanning a QR code by hand is easy when you don't have the phone handy. (sarcasm)

That's way different from "I don't want to give out my phone number".

Both are impossible when not having a phone.

It's non sequitur.

"I have a phone number but don't want to give it out" is different than "I don't have a phone".

But hey, there are 2FA devices you can use instead.

This is why I'm a big fan of the U2F standard, which allows a device (generally a small USB/NFC device) to generate shared secrets for arbitrary services without exposing any personal information.

Think about this problem in context with the NIST trust level framework.

Nobody gives a shit about low trust environments... go ahead and crack my slashdot account, but higher trust stuff like mail, money, network access etc absolutely need MFA.

That's my point. MFA itself is certainly a very useful security solution (for example, I wouldn't trust a bank that doesn't use it), but "MFA everywhere" is not a way to go, because I value my privacy more than some useless Internet account.

A security key should work.