Sorandra over on Livejournal has an interesting bug happening when she runs WoW in Vista-- her female draenei is showing a different skin in different situations. Out of water, she's got the face you see up on the left. But in water, a different face appears. It looks like her toon just really hates water.
Of course it's just a texture error (a known one, at that), most likely fixed by updating her video drivers. But it does kind of make you wonder a little bit why Blizzard doesn't bother implementing something like this for real, and making characters actually show facial animations. Sure, the mouths move, but we can't actually frown when we /frown or smile when we /smile. If it's this easy to change the face textures, it seems like it would be just as easy to show displeasure for real.
The only obstacle might be that they'd have to design different textures for each gender and race, which would take a bit of time (time probably best spent on the actual patches and expansions). Still, a little more emotion would be fun to have. If Blizzard ever gets around to doing a graphics overhaul (much like Dark Age of Camelot has done with one of their expansions), hopefully something like this will be on the list.