Here is a really cool demonstration for facial deformation based on joints and corrective PSD (BlendShapes) by Andy van Straten. The pose space deformations are triggered by several controllers in the setup. The combination of joints and PSD gives some great facial deformation to this character or let’s say a facial deformation masterpiece. Really liked it!

Below is the video demonstration by Andy on how he actually setuped the PSD and overall facial rig. Really neat stuff!

P.S. “cvShapeInverter Tool” By Chad Vernon. For creating corrective shapes…. ultra fast!
http://www.chadvernon.com/blog/maya/free-cvshapeinverter-tool/