My Nikon D700 is 6 months old and has had the same (new) lens on it since it came out of the box ( and it's never been taken off )
I've just photographed some people skydiving ( from the ground looking up ) and got home to find a series of grey dots splattered all over an otherwise clear blue sky - a quarter of the frame looks like it has measles.
I e-mailed Nikon's service department ( and sent an example image ) and they offered to charge me £30 to clean the sensor.
Thank you Nikon for selling cameras with a manufacturing and design issue that render them virtually useless ( and a serious liability in commercial terms ) and then asking customers to pay for sorting them out whilst they are still under warranty.
Not sure of the facts? Type 'oil' and 'Nikon sensor' into Google and see how many people have encountered the same problem.