According to an Apple Retail insider, only:
about 50 percent of Apple Store customers who need to get their iPhones swapped have never plugged them into iTunes after the initial activation and sync. This is a big reason, according to this birdie, for why Apple Store Geniuses are excited about iCloud.
Apple will be incorporating automatic iCloud and Wi-Fi syncing in iOS 5 this fall for iPhone 3GS, iPhone 4, iPad 1 & 2 and iPod Touch 3rd and 4th generation.