Blizzard wants make the authentication process less intrusive and this is a first step towards that goal. Right now, having to input a code each and every log in is a pain, sure, but it also makes me feel secure. I'm never going to say no to more security, however, and if the system is something that can accurately figure out where I am and let me on, that's great.
This doesn't take into consideration the circumstance where you use an authenticator to prevent access to WoW, even from the home PC. I know some parents who use a simple password that their kids can remember but use the authenticator as the gate to prevent unwanted play. Maybe there will be an opt-out feature of some kind to always ask for the code.
You can check out the Battle.net account security page or check out the Blizzard mobile site for application information. For more information on this specific change to the authenticator system, follow me after the break.