Ever watch a movie where there are multiple storylines that converge at the end? That sort of happened for me this week, though not on the big screen. In Washington D.C., representatives of Facebook, Google and Twitter testified before Congress on their advertising policies, trying to explain how millions of Americans saw placements from Russian-backed groups. In Kentucky, horseman Tom Gentry died. Those two items do not seem related. Stay with me. The next morning, on National Public Radio, Randall Rothenberg, president and CEO of the Interactive Advertising Bureau, a...