They should make it part of your training to warn you that not everyone is friendly. After all don't they have to pay YOU to be friendly? And customers don't ask to be greeted, so we are therefor not obligated to respond. I especially would not respond to a fake smile. Females usually won't respond when they think the guy is creepy, not when he looks good. I'm just saying. And I personally have never seen a sign with sensor protocol, so you can't really expect everyone to automatically know what to do. You know what annoys me? Door greeters.