But the complaints also mention that the e-mail conversation was archived (what they actually said sounded something like it was irreversibly disappeared, which might just have been a mis-observation). So the prospective employer or whoever might have been trying to respond but the original sender was never seeing that, so thought the recipient was giving radio silence. And if the recipient was responding but the originator wasn’t seeing it, then the recipient might have also thought the originator had lost interest.
I also saw one tweet complaining that the regular “Send” button was doing the same thing. So there was some suspicion that Google’s prank was not only a Bad Idea, but also buggy as well.
ETA: I also saw one tweet that someone had sent a condolences message to a friend who had just lost a close relative, and this gag got attached to that.