Most people will have to sync their passwords (generally strong and unique, given that it's for github) to the same device where their MFA token is stored, rendering it (almost) completely moot, but at a significantly higher risk of permanent access loss (depending on what they do with the reset codes, which, if compromised, would also make MFA moot.) (a cookie theft makes it all moot as well.)

The worse part is that people think they're more protected, when they're really not.