Your comments were already censored an hour ago. Hopefully, my comment will survive. You can contact me at justin.evans @ brytewerks.com. I will happily testify on your behalf. I've had my screen replaced FOUR TIMES. I'm a mechanical & systems engineer and work with these products every day; I know exactly what is creating the problem.
Most of the people on here have good intentions but they confuse what they observe with science; the problem is a poorly conceived air filtration system combined with high-humidity environments. Living in Florida, the tropics, summertime in the midwest or using a humidifier is the catalyst because dust particulates in the air contain enough excess moisture that they clump up behind the LCD panel and accumulate into what look like giant stains.
The solution for Apple is simple; a removable HEPA filter in the base of the iMac would filter out particulate down to 3 microns. One simply pops open the HEPA filter's cover, removes it, rinses it our or replaces it and the problem would not occur.
Instead of solving the problem Apple would rather censor this thread. It is the worst kind of incompetence. So, yes, I will gladly testify for you. Email me before this message gets deleted. You know the idiots who censor this thread will delete this very, very soon.
I've been part of this thread for nearly two years. I was one of the original people complaining about the problem (and originally thought it was a heat issue.) Each time my "screen goes bad" I've studied the problem in greater detail. Since I have AppleCare I demand they repair the system in my home and I thoroughly document the repair process. Its amazingly simple; they just remove the glass bezel, carefully remove the LCD panel and then replace both...without dusting the system or addressing the real problem. Inevitably, the dust spots return. I've wiped the dust with my fingers; it is clumpy due to moisture.
Apple loves to point a finger at you the customer. "Well, perhaps it is a lifestyle issue." Sorry, Apple, living in Wisconsin or Florida isn't a legit reason for you to dodge a basic engineering flaw!
People have blamed cigarette smoke, heat, pressing too hard on the LCD panel (which is just dumb; you're pushing against thick glass and can't affect the LCD panel at all with pressure) and a variety of other pet (and scientifically unsound) theories. It is so amazingly simple: its just the unfortunate collision of humidified dust and poor filtration. The reason Apple doesn't fix this is because they don't know how to properly isolate the problem and test. This isn't a conspiracy of geniuses...its a conspiracy of dunces. They aren't out to get us...they just don't know how to fix this. They designed a beautiful computer in a low-humidity environment and have never spent enough time on air filtration.