So a while ago I ran across this spanish commercial by 23 lunes.
NEOsitrin 20" from 23lunes on Vimeo.
and I was following the rabbit trail and on their vimeo site saw this TD rig by David Corral
23lunes - Technical Reel 2007 from 23lunes on Vimeo.
which was really interesting to me because after he does the regular blend shape based facial rig, he throws up a joint based one. I assume the skin is weighted to joints, and the joints pivot point is placed in a space where when rotating the joints maintain the volume of the head (like you would with a joint for the eyeball.) What I thought was extra clever was the set driven key on the blenshape to kick up the wrinkle once the joint has moved a certain amount. Seems like this style might give you a lot of crazy potential.