Kind of a reverse situation here... I have an old Firewire charger for previous generation iPod... I've read that they are 'safe' to charge the iPhone.. but when I hook that up to the iPhone, I can actually hear the battery/phone emit a high pitched whine... where the USB charger does not. I can't imagine Apple would not put a safeguard in place to be able to use the old 12v chargers... but that whine made me concerned...
Anyone else experienced this?