How to disable iPhone's back up process ; Jason Chen

We've noted in our iPhone 2.0 software review that iTunes' full image backup of your iPhone when you've made changes to what apps you've got installed can take a really long time. We're talking tens of minutes. If you're the type of person that doesn't really store anything important on your phone that can't be reinstated from your contact list or calendar or elsewhere on your computer, Zero Logic found that you can actually skip this process.
Two caveats to this. One, you shouldn't interrupt a backup that's in place, because that results in a corrupt backup. It's fine if you perform another backup right after to make a correct one, but if you forget and try and restore? It's phone corruption time. Two, using this method means you will not have a phone backup. Yeah, seriously. You won't have anything to restore from, so you'll have to go in naked the next time something's broken with your OS. Now that you know what the risks are, here's how you do it:
This command will change a hidden setting in the iTunes preferences that will force it to skip the backup process.
1.-Quit iTunes.

2.-Open Terminal.app

3.-Copy and paste this in, then hit return:defaults write com.apple.iTunes DeviceBackupsDisabled -bool true
4.-Open iTunes

5.-Plug in your iPhone (2.0 or 3G) and sync.
It will take a few seconds, assuming you don't have a ton of music or podcasts.
Changing the 'true' in step 3 to 'false' will re-enable the backup feature.