Well, let me tell you, I've got a different idea. I've seen the close up of that statue and the little guy seems to have a impish grin on his face. I think old Neb-Senu is simply messing with us. None of the other statues on the shelf are being turned by all that differential friction and daily vibration. Neb himself was impervious to the vibrational influences for decades. No, Neb is messing with us, pure and simple. Inanimate objects just like to do that, sometimes.
For instance, tonight, I dashed into one room to answer the ringing phone. The room was dark. I reached for the overhead light's switch, which I've hit thousands of times flawlessly in the dark ... and it wasn't there. I lunged for the ringing phone ... and it wasn't where it should have been either. That wasn't an issue of friction, vibration, and foot traffic. No, those inanimate objects were messing with me and messing with me good. It was a tag team messing! I had to dash off and find another phone in a lighted room to take that call. I could almost hear faint giggling behind me from the darkness.
Others say Neb-Senu moves because it's the curse of the mummy. If that's so, the mummy's curse sure isn't all it's cracked up to be. "You have been cursed by the mummy! One ten inch stone statue will now rotated unexpectedly in your museum ... forever! Bwa ha ha!" No, not too impressive at all!
I predict, now that he's gotten some good attention and media coverage, Neb-Senu will mysteriously stop turning entirely, passing the baton off to some other inanimate object to mess with us in some very different way. Yeah, you just can't trust those inanimate objects. They're out to mess with us.
Just ask Battlestar Galactica fans about toasters if you doubt me!
For another theory of mine, see: http://jsbrookspresents.blogspot.com/2009/05/alien-abductions-and-slavering-monsters.html