Just to put this to bed, here is what happens when you get moon dust on a lens at f/16.
http://www.hq.nasa.gov/alsj/a12/AS12-46-6818HR.jpg
http://www.hq.nasa.gov/alsj/a12/AS12-46-6826HR.jpg
http://www.hq.nasa.gov/alsj/a12/AS12-46-6813HR.jpg
The camera is behind an optical window that can withstand immense pressure, meaning it is probably spherical. Since this protrudes from the underside of the ship, it's very possible that it can become smudged with whatever detritus it is maneuvering around in.
Really, has conspiracism just become a given fact of modern life? Sometimes a cigar is just a cigar.