So it's a survey in a chat window? I don't see how this is any more or less annoying for either side. If anything it sounds like this one is more invasive.
Now people are used to "WhatsApp" or messaging kind of UI than a normal form filling experience. The reason is those experiences provides by WhatsApp and FB messenger are more engaging. If we engage the survey takers, the completion rate will improve, that the whole funda behind a conversational experience
I can't help but think that after the third WhatsApp survey people will no longer think "what a novel experience", they'll be used to it and think "Yet another survey...".