>>Yesterday I was in the local Best Buys ... Both cameras were in the on position, and both cameras had no lens attached and the lens area cover was missing.
I've seen the same thing at my local BB. I would never buy a display model from a big box store (especially BB).
But in any walk in retail store any camera could have been shown to a customer and left laying on the counter for some time, lens mount up and open.
Just to say I don't think it is fair to blame dusty sensors on Nikon unless you know for a fact the camera was never touched at the retail level- and we could never know that for sure no matter who we buy it from.