There was some brouhaha in recent years over lens coatings and filters. Covering all manners of uses from toning down chromatic aberration to sorting out moiré patterns. Nikon has recently published a video demonstrating the purpose and effectiveness of their fluorine coating to be found on some of their lenses, and likely, many more to come.
Not to be confused with the Nikon Fluorite lenses which have a fluorite coating in an effort to correct chromatic aberration, especially for lenses of a longer focal length, the Fluorine coating serves the purpose of repelling foreign debris; could be water, grease, dirt, or even permanent marker as suggested in the video.
Both Canon and Nikon have this sort of technology, though Nikon, via graphs and such, try to explain how much better their coating is from competitors. I like the idea, I really do. I think this sort of coat in should be standard, and for that matter, I wish it was standard on the rear LCD!
Original Source: Imaging.Nikon.com