A WhatsApp acquisition was always going to be on the cards and Facebook was always going to be in contention to buy it. The real question is going to be “what next”. Though everyone is saying it’s business as usual and WhatsApp will be run autonomously from Facebook, these are all utopian plans and rarely happen.
I’m not saying it’s “Facebook will take over the world” thing as in the tale of Instagram, nothing will change well apart from the rights grab on your photos and the resulting backlash of user rights and terms.
Remember, you are the product not the customer.
Anyway, putting my Nostradamous hat on for a second the obvious choice is in message ads being served up between two chatting friends. With some basic machine learning it’s easy to figure out over time what sort of things they are in to, where they are via location based services and the facilities nearby.
All it needs is some Facebook savvy retailer to put the ads on and let the WhatsApp/Facebook combo do all the heavy lifting.