Interesting discussion thread.
In the part of the world I live, Whatsapp is used for lead nurturing.
I once showed mild interest in purchasing a property that was too expensive for me, and I got sucked in lead qualification and nurturing process. The real estate agent consistently sends me properties that are out of my price range through automated messages. What is bad about is, the sales team have not even qualified me as a lead yet, because they never really asked me why I didnt buy. Obviously price and financing would be a major factor in real estate purchase decisions but they seem afraid to address the topic. They settled with bombarding me with messages twice a week of new offers of houses I cannot afford. About a couple weeks ago, I ended up blocking the person on my Whatsapp.