This is one end-game of AI - changing the economics of scams.
Imagine how a 'long con' works today: a scammer befriends a person online through a video game or social platform, and develops a rapport with them over the span of days, weeks, months. After some trust has been gained, the scammer then requests money from the victim. Does this happen a lot today? I don't know, but certainly one reason it doesn't is the economics of the scam. Who wants to spend a significant period of time gaining trust just for the chance of a payout?
AI is going to flip this on its head. Rather than dedicating hundreds of hours of a scammers time, a scammer could instead use a system like Duplex to befriend hundreds or thousands of victims simultaneously. Let it run for a few months, developing a strong rapport with the target, until the AI finally requests some money from the victim.
Yes, duplex is for completing specific tasks, but how much of a difference is there between "Duplex, book a table for four at 8pm" and "Duplex, ask my victim about how their day was"?