Its true, this issue needs to be discussed more openly and a lot more people need to know about the problem - because it really does degrade the value, and overall utility, of what could/should be a premium hardware product. I just paid eu2500 for my new rMBP 4 months ago and it already looks like its going moldy ..
My best guess (typing this on a screen that has those exact issues) is that the screen is reacting to salt and oil from hands. My previous white macbook had the same (but worse) problem. I think any glossy screen had this problem but maybe I'm completely wrong?
i had this happen on a macbook i used some weird cleaning agent on the screen with; this was maybe 3 or 4 macbook's ago -- since then i'm really picky about what i use to clean the screen, and i haven't had the problem.
obviously it's not definitive, but i suspect cleaning products may be to blame, or blame in a large number of cases.
Having worked my way through an engineering degree as a lab manager for an optical lab, this looks like what happens to an A/R (anti-reflective) coating when harsh cleaning chemicals are used (Windex, etc...).
On mine, I would just use a water-dampened, clean, soft towel if I need to clean my screen. And by clean towel, I mean clean. I don't even set it on the counter as it can pick up particulate matter. And by soft, I mean never a paper towel. Ever.
Yes this is what Apple says. The fact is that all screens have serious structured patterns imprinted from the keys - independent on the cleaning method.
Buyer beware!