Wall Street Journal: What if you could replace most of your web searches and apps with a single interface that just gets things done? That is the premise of Facebook’s new “M” — a “digital assistant” available through its chat app, Facebook Messenger. Still in beta, M is only available to approximately 10,000 people in the Bay Area. If M works, it could mean Facebook will open up a major new front in its battle with Google for your attention, and in the process give the social-networking site access to a gigantic pool of direct-response advertising dollars.