This year, we learned to love AI assistants in our homes

This year, many of us let a stranger into our homes and ended up loving it. I am, of course, talking about voice-activated artificial-intelligence assistants. The success of Amazon's Alexa, the launch of Google's Home, and Mark Zuckerbrg's public quest to build his own digital butler all demonstrate that conversational interfaces, which we predicted would be a breakthrough technology in 2016, are here to stay. Amazon's Echo smart speaker, which is a conduit for the company's Alexa AI assistant, was officially available to all in the U.S. from 2015. But this year it also went on sale in the U.K. and Germany, and estimates suggest that it sold as many as two million units in the first nine months of 2016.