I think they bought it purely to prevent it evolving into a competitor. It's got too many users to kill off as a product, and at least they are 'Facebook' users

I think they bought it purely to prevent it evolving into a competitor. It's got too many users to kill off as a product, and at least they are 'Facebook' users in a roundabout way, and by not adding anything anything new to WhatsApp they can keep it subjugated. Keep your enemies closer and all that.