I may be misunderstanding your argument, but I think the parent argument still applies whether you are getting served by a human or being served by a machine wh

I may be misunderstanding your argument, but I think the parent argument still applies whether you are getting served by a human or being served by a machine which has the same "one checkout at a time per person" kind of bottleneck that a human has. Edit: The "scan your own cart" model is a more compelling counter-argument than the self checkout machines currently at Wal-Mart, as this can accommodate a much higher throughput.