Turmoil in the US video market this week, as reports are flying out of the woodwork to illustrate the shifting sands on which media and entertainment is built. FAST (free ad-supported streaming TV) users have already overtaken traditional pay TV subscriptions in the US, and the latest set of quarterly results suggests that if current trends continue, virtual MVPDs (vMVPDs) could hold more subscribers than traditional MVPDs in just three years. vMVPDs have now carved out one fifth of the US pay TV market, according to new quarterly numbers from Leichtman Research Group (LRG). LRG says that the top four vMVPDs in the country added a little over 1.3 million subscribers across Q3, amassing 14.7 million subscribers in total. YouTube…