Facebook COO Sheryl Sandberg says the $19 billion WhatsApp acquisition was the right decision as the mobile messaging service has huge potential for growth and will soon have a billion users. "Real time messaging is really important and WhatsApp is one of the very few companies in the world that is on a path to a billion users. Even since the acquisition they've hit over half a billion users. They are hugely important here, everywhere in the world. We're excited to work with them".