I asked this question to the salesman when buying my D70 and he looked at me like I was nuts not wanting to protect my lens. So I have the UV filter. Have not noticed anything bad about them. I thought they may reflect light back as that has happened a long time ago when using film and doing time releases.I guess only under ideal conditions would I risk keeping the filter off the lens.

"The happiness of a man in this life does not consist in the absence but in the mastery of his passions."