In 2014, WIRED asked me to write a few lines about my most-used app as part of an internship application. I wrote about WhatsApp because it was a no-brainer. I was an international student from India, and it was my lifeline to my family and to my girlfriend, now my wife, who lived on the other side of the world. “This cross-platform messenger gets all the credit for my long-distance relationship of two years, which is still going strong,” I wrote in my application. “Skype is great, Google+ Hango...