In regard to the purchase, Ben Thompson has a good piece:
This is why I 100% believe Jan Koum when he says that WhatsApp will remain autonomous, at least from a product and branding perspective. To glom WhatsApp onto Facebook-the-product would be to throw away exactly what makes WhatsApp valuable to Facebook-the-company – that it’s not Facebook-the-product. It is better to think of Facebook-the-company as a conglomerate: Facebook-the-company builds, acquires, and manages multiple products that serve all the different segments of social. The largest and most well known product in their portfolio just happens to be called “Facebook” as well.