[jfv]

I feel like this is going to make the world even flakier than it already is. If I can waste people's time without even the few minutes it normally takes to make a phone call, what's to stop a restauranteur from effectively denial-of-service attacking competing restaurants, or what's to stop me from booking 100 dinners for Friday evening because I'm not exactly sure what I'm going to want to eat (or who I'm going to take out for that matter -- smartphones make it easy to punt on that decision too), so I retain optionality.

[MichaelGG]

What stops a restauranteur from abusing Google's Gmail service? Presumably Google won't allow you to do spam with Duplex either.

If you are going to be more enterprising then you can already do this. Just put some HITs on Mechanical Turk and let them place calls. Should cost you a few bucks to flood hundreds of calls.

[jfv]

I don't need reservations that badly. But the difference between having to specify Mechanical Turk work and just talking to a Google appliance is pretty huge... We're talking hours vs. minutes of work.