Idk why but my Macbook pro have one tiny spot which reminds the iPhone 6's oxidation issue. I never ever put anything on my macbook near the trackpad but my hand. It is very weird experience but I found that there are few more people having similar oxidation? issue. Mine is Late 2013 Macbook Pro 15inch. It's not really a big issue but I assume that Apple's aluminum seem to be suck to me especially with iPhone 6S. There was another thread relate to oxidation issue on Macbook series in 2011. Apple! Do something about aluminum itself!!