Unfortunately it's the only two factor authentication system that's going to work for the public at large. It's a simple system that works with any and every cell phone on the market, with no need to (re)develop applications for multiple OSes, manage syncing those applications to a master server, and then handle user support issues when those applications break.
The problem with "proper" security is that it works against the user. Long passwords that you can't remember, SecurID tokens that you never have when you need them, and finicky fingerprint readers that are too easily fooled by fakes. And in the end, all of this just gets subverted by social engineering, calling the help desk and convincing the rube on the other end to reset the account password. Unbreakable security fails at being friendly when faced with the fallibility of users, and at the same time it's only as strong as the weakest human who has control over it.
The fact of the matter is that the only real threat to PSN users is going to be criminal gangs harvesting accounts en masse. A token two factor system, properly implemented, is going to be enough to stop that. It's security that's good enough. Otherwise you'll quickly discover first-hand how perfect can be the enemy of good.
Which is not to say I advocate poor security. But so far no one has come up with a better way to do it. It has to be universally compatible and it has to handle user failures gracefully, and there are very few ways to do that.