Maybe its what you are doing on the iMac?
For the thousandth time NO! People seriously stop coming in on the end of a thread and commenting out of ignorance. Read the entire thread start to finish before commenting.
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it's kind of bizarre
like when people show backlight bleed and crank up the brightness to 100% I'm like WTF? how is that relevant because no one ever uses brightness at 100%.
No one EVER uses 100% brightness. You're right, Apple should put out a bulletin. NO ONE SHOULD EVER TURN UP THEIR BRIGHTNESS TO 100%, OUR PRODUCTS MIGHT SHOW A FLAW...
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People here are weird. Normally nobody wants problems but here they are actively seeking for them

As usual most will only see a "problem" after jumping through lots of hoops such as displaying a checkerboard.
As for image retention or burn-in....lot of people seem to be thinking this was a CRT problem which doesn't exist in LCD/plasma panels. You couldn't be more wrong. Every LCD/plasma panel is prone to this problem and yes that means IPS as well as TN too! It's a huge problem when you do narrowcasting since most TVs use a TN panel or some other LCD technology. Same thing for those big screens that are used to display some nice statistics. If you always keep the same windows open in the same positions or display presentations that all have the same theme you'll eventually end up with burned-in images. Burn-in is something that you prevent by displaying different images and different presentations using different themes. Using a screensaver was a must back in the days and it has never changed.
I naturally move around my windows when I work at the computer. Not to prevent burn-in but simply because it's more convenient at that time to have the window a certain size and at a certain position. I'm also using a screensaver and have OS X set up to ask for my password when interrupting the screensaver. This is one of the ways to lock your computer in OS X, Windows, Linux, etc. Whenever I walk away from the computer I lock it (at work this is mandatory due to our certifications). I suppose this has been a very effective way to prevent burn-in.
I wasn't "looking for a flaw". The flaw found me. And I guess I will say it yet AGAIN. Read this entire thread, start to finish so you can become more educated thus giving you a better likelihood of having an applicable response. Once a person is AWARE of the flaw, it becomes easier to spot. Which goes back to what I said before. Ignorance is bliss. For some reason Apple people tend to fall into that category. God forbid they find out there might be an issue with their precious product. Oh no, now we must defend the Apple gods tooth and nail regardless of how idiotic and fanboy like we start to sound. Let me put it simply. THERE IS AN ISSUE WITH THE IPS PANELS THAT APPLE IS GETTING FROM LG. Now I don't know if it is ALL or SOME, but there are issues. This issue was not as apparent when Apple was sourcing both Samsung and LG for their panels. Coincidence? I think not. Have a Google search. It will do wonders for you!
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it's kind of bizarre
like when people show backlight bleed and crank up the brightness to 100% I'm like WTF? how is that relevant because no one ever uses brightness at 100%.
Try this one on for size...
"Apple is facing a potential class action suit in San Francisco's California Northern District Court after an owner of its MacBook Pro with Retina display accused the computer company on Wednesday of 'tricking' consumers into paying for a poor-quality screen, citing an increasingly common problem that causes images to be burned into the display, also known as 'image persistence' or 'ghosting.' The lawsuit claims only LG-made screens are affected by this problem, but 'none of Apple's advertisements or representations disclose that it produces display screens that exhibit different levels of performance and quality.' Even though only one man filed the lawsuit, it can become a class action suit if others decide to join him in his claim, which might not be an issue: An Apple.com support thread for this particular problem, entitled 'MacBook Pro Retina display burn-in,' currently has more than 7,200 replies and 367,000 views across more than 500 pages."
"They used to get their displays from Samsung. They switched to LG, now they get **** LCD's. The first lot of Retina displays all came from Samsung. Apple got a reputation for having really good screens in their retina product line and have now switched to the lowest bidder, at the expense of quality."
"I followed some of the threads on this on MacRumors. Problem: A lot of the users there will automatically and unquestioningly attack anyone who suggests that an Apple product is imperfect in any way."