I don't know what kind of metal Apple used on the MagSafe connector (metal part), and I had it knocked on my MBA twice and each left a tiny ding/nick on the aluminum case when I unplug it and try to roll up the cable and the cable some how just swing around. Both hits were on the edge of the machine. It was pretty light knock and it'll take away some the of finish. It appears that the connector was made of some material that's harder than the aluminum body. Keep the MagSafe connector away when it's not plugged in. Having clear skin on my MBA did not help, it cover like 95% of the area but the MagSafe chosen to knock on the area where the skin's not covering. Kinda render the skins useless in a way. Oh well, I can sort of enjoy my MBA more freely instead of baby it like a crazy guy.