Issue with 2FA is that you are forcing people to go with Google, second, people who travel past their cellphone area code with surcharges, and I found it caused me grief when I traveled abroad.
Also 2FA security has caused security hacks in the US where some folks called the cell provider of the target victim as a provider rep and got the sim card and now had full access.
Completely agree. It just isn't a benefit when used on a private wallet which should already be 100% secure. It could easily cause problems if you lose your phone, or don't have it with you.
+1
In that case, how about - upon installation of the wallet and generation of the PrivKey, wallet asks user if he/she wants a 2FA on a USB. If user clicks YES, generate an authentication key on a USB (which can be cloned for 2nd or 3rd backup), in a similar manner that a full-system encryption via USB as a 2FA is done. similar to-
http://blog.refu.co/?p=1398