This won't necessarily be free. WhatsApp is working on a free WhatsApp Business client for small operations, and an "enterprise solution" for large-scale companies. Your airline of choice will likely have to pay, in other words, but the corner store probably won't.

You probably won't notice this if you live in places like North America, where you're more likely to use Facebook Messenger for business chats, but it could make a big difference overall. WhatsApp practically dominates messaging in some parts of the world (such as India), and many smaller businesses already use it to talk to customers. An official notification system could give those tinier outfits the kind of tools normally reserved for bigger companies, and it might give bigger firms an incentive to reach customers in a more immediate way than email.