I had this occur with my 2004 PowerBook back in the day, it was pretty bad. At the time I had found a company that made adhesive transparent stickers that you c

I had this occur with my 2004 PowerBook back in the day, it was pretty bad. At the time I had found a company that made adhesive transparent stickers that you could place on either side of the trackpad that would protect the aluminium from being eaten away by the sweat on your palms. I bought this when I upgraded from my PB to my Core 2 Duo MBP in 2007, fearing that this newer machine would suffer the same fate as my PowerBook, but all is well and that machine didn't experience pitting. Having said that, the pictures in the link are pretty bad, I've never seen pitting that bad before, that looks horrendous!