[frankinstien]

I had this very same idea for a social robot where the face is projected onto a semi-transparent or frosty faceplate that is in the shape of a human face.  Here's a company doing just that and its called Furhat:

[infurl]

Several of the robots portrayed in the 2001 movie "A.I." by Steven Spielberg looked like that too. It was extremely effective.

[WriterOfMinds]

That's clever. Most of the expressiveness of a human face, with a lot less intricate hardware.