I use my Air and used my old Macbook (the white plastic one) in my workshop, where we make shoes by hand. So I have lots of nails (and thus, lots of tiny metal

I use my Air and used my old Macbook (the white plastic one) in my workshop, where we make shoes by hand. So I have lots of nails (and thus, lots of tiny metal scraps from the nail boxes, as well as nail pieces when we need to cut some down) lying around and lots of knife-sharpening dust around our (unplugged, since we usually keep the computer away when hammering/sharpening, but we just leave the connector in his usual place) Magsafes and have seen no problem in the connector.