Hardware keys defeat all remote attacks. TOTP defeats remote bulk attacks but not targeted real-time phishing. SMS defeats almost nothing determined. 4. The Recovery Problem: Your Backup Plan 2SV adds security but introduces a single point of failure: losing your second factor . If your phone is stolen, factory reset, or broken, and you only had TOTP on that device, you are locked out permanently.
2SV is not about being paranoid. It's about raising the cost of compromise from trivial to extremely difficult. The vast majority of account takeovers target low-hanging fruit—accounts with only a password. Don't be low-hanging fruit.
2SV adds a second, independent factor: (a device, hardware token, or phone number). Even if your password is compromised, the attacker still needs physical possession or control of your second factor to log in.