In a recent article on WoW.com, they discussed the upcoming iPhone OS update, but warned also that if things were to go wrong that you should probably write down the serial number found in the authenticator so as not to lock yourself out of your own Battle.net account.
Read up on the article if you own an iPhone or iPod Touch. I know a few of my guildies have it. I'm sure to write down the number in my phone, just in case. :)