I do find this new approach to authentication somewhat disturbing for two reasons. First and foremost, usability obtained through the sacrifice of security bothers me, though I believe the jury is still out for this scenario. I would argue that man-in-the-middle attacks against SMS messaging are growing and will lead to further compromise of these types of authentication mechanisms.
Secondly, I believe this type of authentication can and will continue confuse the conversation around two-factor or multi-factor authentication. Two (or more) – factor authentication is, in my opinion, a necessary next step for general consumer and corporate security. Anything that confuses that conversation is detrimental.