I was just about to try it, but the idea of allowing Firefox access to my audio/video to talk to a machine-generated person gave me such a bad feeling, I couldn't go through with it even fuelled by my morbid curiosity.
I did it. The demo is kinda cool. If they want to steal an unshowered, back-lit, messy hair picture of me, go for it. I can't imagine it'd be that useful right now.
I did it with my finger over the camera and it even commented on me having my finger over the camera!