No, since it's entirely up to them to carry on conversation. Forcing it has its merits with getting to know each other but in general it's tedious and sometimes downright agonizing.
If someone does that I wouldn't choose to prod unless it was a pretty deep discussion about something that ended abruptly. It's increasingly common that people think they replied but actually did not.
it's entirely up to them to carry on conversation but can't they at least say they don't feel comfortable and end it that way is the question. but then again, I should be more understanding that it's probably their anxiety that they cannot even say so.