Forgive my ignorance, but I always thought the point of using SMS was to avoid using the same data channel for transmission, kind of like having Fiber with a ba

Forgive my ignorance, but I always thought the point of using SMS was to avoid using the same data channel for transmission, kind of like having Fiber with a backup DSL/Cable line for a small business. This innovation sounds awesome, but is Twitter exposing their clients to additional risk by returning to a single communication channel? I suppose that Two-Factor isn't designed to withstand a carrier-based MITM attack, and that such an attack would probably apply equally well to data as well as SMS, but I think it's interesting to model the attack surfaces. All in all I think this is the right direction for Two-Factor, but I wonder if there's a way to use something other than the carrier data channel to deliver the second-factor. There's something to be said for using a diversity of transmission mediums. Something to think about. EDIT: For the sake of clarity, I'm referring to a single data channel in that you transmit your password using your cellular data connection and you would also be providing your two-factor challenge over the same data connection, whereas previously the SMS portion represented two discrete networks for authentication.