It was less than a month ago that I wrote about a trend that should be very worrying for Facebook. Namely, that users were spending less time on the platform. According to Nielsen numbers through November of last year, interpreted by Pivotal, the social network lost about 4% in aggregated time spent. Now new numbers have been released that go through December, and the problem only seems to be getting worse. The updated data shows that Facebook’s core platform lost 18% in time spent, which is a huge change from the month before. This, says Pivotal, reflects a 24% decline...