I went to WalMart a week or so ago to get one thing, and the self checkout line was empty...figured that was as good a time as any to give it a whirl; it was slightly daunting, but doable.
This thought just popped into my head: What about a liquor or cigarette purchase? How will they "card" the customer? A gong probably goes off, and then you get to enjoy waiting for a humanoid to show up...