Hands Free Etiquette

You'd think after being around hands free devices for however many years now I'd be used to seeing someone walking down the hallway at work, alone, with both hands in his pockets, and seemingly talking to himself. Or you'd think glancing around in a traffic jam and seeing someone talking with both hands on the wheel and no one else in the car wouldn't strike me as strange. It still does. I'm still looking for someone to be holding a phone to her ear to determine if she is on a call or not (and if it's appropriate to begin speaking to her). How long will it take before we look for the tell-tale blinking blue glow surrounding one's ear instead?