Now before you all tear into me, I'll just relate a conversation I had today with my Nikon dealers top repair tech.
I decided that I don't really need to eat this month (or next) so I went to town (literally) and visited my Nikon dealer to see how easy it would be for him to sell me a 70/200 f/4. In the event, not long at all...but that's another story.
While I was waiting, their camera tech was wandering around and we started talking - not unnaturally, considering what we're reading on the web at the moment, talk eventually got round to the 'oil' spots on D600 sensors. "Rubbish" says Francis, " this is complete nonsense - Nikon (and almost all the camera manufacturers) have been using electronically timed shutters since the early 80's and they discovered very early on that greasing or lubricating any of the mechanism actually tends to clog it up eventually, rather than make it run smoother. To this end, they simply do not lubricate the shutter systems. In addition, when the mirror rises, it has to reach horizontal before the shutter is allowed to open - so any lubricant would have dropped to the floor of the mirror box before the shutter has opened far enough."
He went on for a while, ending up with his opinion that it was far more likely due to poor cleaning/lens changing protocol standards etc. etc. At this point I felt I'd better just smile and nod my head - after all, I might need him one day (!!) but what he said did seem to make sense - I obviously cannot vouch for what he says as I'm not in the business, but I have to say it all sounded reasonable.
Just though I'd pass this on...(ducks to avoid the anticipated salvos....)