re: Twitter Two-Factor Lockout: One User's Horror Story
The problem is that two factor authentication mechanisms insist on using a smartphone. There are plenty of other alternatives such as PC, tablet, landline, or even snail mail plus authentication questions that the user creates and, of course, answers. I would never use the "Name of first pet" question because I did not have pets growing up and many of the other questions do not allow for the correct answers because for me they include special characters that US designed systems are too dumb to handle.
That all was to be solved with the backup codes and I think it is a goo approach. If users are too careless to take care of the backup then oh well, they are out of luck. In the end this is just a Twitter account...who needs Twitter anyway?