I have read a few places that you should keep rigs between 30 and 64 bones for a mesh. To be honest I am not sure how to do this on a character with fully articulating hands and a face rig. My face rig is fairly minimal: four bones in the lips, four in the brows and two for the tongue (the eyes are sort of fixed orbs). But…
If you want full hands (don't forget that the hand itself can also bend as the metacarpals move, though usually 1 bone in the hands is ok) it looks as though you are going to be riding that limit. Is this a limit for an engine you are working with or just a random guideline? These things are very engine specific, usually.
I really hope morphs replace bones for facial animation during the next hardware cycle. They are so much easier to work with and such a wide range of expression can be pulled from a handful of morph targets.
It depends on the game engine you are using, and the type of game you are working on. 30-64 is the advice from several years ago. These days I would say between 60-128. For Age of Empires Online we used between 16-28 bones per unit, because they were so small. For Orcs Must Die because there were so many enemies on the…