Please dumb this down for me. My wife wanted to know if all USB powered devices (iPods, iPhones, etc) could share cords and more importantly, share the AC or car adapters that u can plug the cords into. She confused and so am I about how some cords have different watts and what that means exactly. Can u hurt one device by using the wrong watt and what about those cheap plug in to car lighters, is it safe to buy them and plug any USB cord into them? Thanks for any info.