iPhone 3G: Disable iTunes backup - mac

1. Quit iTunes.
2. Open a Terminal (Applications > Utilities > Terminal)
3. Type or copy the following command:
   defaults write com.apple.iTunes AutomaticDeviceBackupsDisabled -bool true
4. Open iTunes.
5. Connect the iPhone.
6. Make Sync without backing up.

To enable automatic backup in iTunes again use this command instead:

defaults write com.apple.iTunes AutomaticDeviceBackupsDisabled -bool false