TLDR: MBPr screen coating is vulnerable to damage through normal use. Wipe regularly. Use protector. Or don't buy.
I have a similar problem with my 2012 retina macbook pro 15'', which is rapidly getting worse. The coating is coming off in the middle of the screen. Initially it looked like a stubborn greasy print from the spacebar. I have been wiping keyboard prints off the screen with a microfiber cloth from time to time, occasionally with the help of Hama lcd/tft/plasma cleaning liquid. I know that Apple recommends only water, but this is disingenuous, as there is no way you can get fingerprint oil from the screen with water alone, and the first thing they did at the Genius bar was wiping the screen with the similar stuff. The solution I have is free from alcohols and I've been using it for years, including on my previous macbook-pro which had an antiglare screen (i.e. no glass).
Anyway, it turned out that the worst affected area corresponds to the region between the space bar and the trackpad. But there are other spots, which are definitely from keyboard key edges. There are also several tiny holes, which I believe are described as "exploding pixels" on a couple of Apple support forum threads. It is possible that the disappearing coating started from these spots, which in turn could have been initiated by dirt particles.
I took the macbook to Apple store. I expected it to be repaired under warranty. However the guy at the genius bar told me that the problem was caused by my negligent use, and is not a manufacturing issue. I agree that it is not a manufacturing issue, but I don't think there was anything negligent about the way I use the machine. As possible reasons the genius suggested excessive pressure or rough particles trapped between the screen and the body. I am carrying my macbook pretty much every day in a soft neoprene case in my backpack, so it is exposed to some amount of pressure, but there is nothing abnormal about it, certainly less than what an aluminium body laptop should be able to withstand. As to the dirt particles, I am sure there were some as I use my MBPr pretty much non-stop in different office and home environments. But if there was a dirt particle are not big enough to be obvious I would get rid of it, and there wouldn't be anything harder than a bread crumb. There was absolutely no sand even close to the machine, ever.
I left the apple store disappointed and confused. After thinking about it for a while and reading several forum threads, I am convinced that the problem is either with the quality of the coating or the design of the MBPr. I will pay another visit to the apple store and try to explain this, but I am not sure it will help. I am afraid that I'll have to either replace the screen at my own cost (~700) or get buy a new MBPr. I'll still go for the Retina (once you get used to it there is no way back).
In any case I am a bit upset with Apple. If extra care is required for the screen to survive daily use (protector, a hard carry case, regular dusting), they should make it very clear. If this is a known problem - and I had an impression from my conversation with the Apple genius that it was - this should be covered by warranty.
Although in the future I will be much more careful, I am sure that I did nothing wrong. It's nice to see that I am not alone, and I hope that there will be enough of us for Apple to admit the problem and/or do something about it.
