D600 dust accumulation time-lapse

Yup, on 20 cameras.  Do you have any idea how insignificant that is relative to total production? They also have no way of knowing how those rental cameras were used.  I've worked in rental departments before, and let me tell you it is awful.  They also did not say they did the exact same degree of testing on all of their cameras.

Why are you ignoring all the problem free D600's which you are FAR more likely to receive? I know of several thousand, and I am just 1 person.

It takes less than 60 seconds to clean a sensor, and you can easily test for this problem in-store.

If they do, it isn't significant enough for them to issue a statement or service advisory. That is normally only done for safety issues or widespread problems.  At this point, obviously the numbers are so small that they are handling it through warranty or free sensor cleanings - the same way every other manufacturer does it.