#0 - June 17, 2009, 6:21 p.m.
Blizzard Post
If you use the Battle.net Mobile Authenticator and intend to update your iPhone or iPod touch to iPhone OS 3.0, we would like to highly recommend that you first back up your iPhone or iPod touch to your computer using iTunes prior to performing the update. By taking this important precaution, you will be able to quickly restore your previous install of the Battle.net Mobile Authenticator if you encounter any issues during the update process.

For more information, refer to the Battle.net Mobile Authenticator FAQ here: http://eu.battle.net/bma