It’s been a rough few weeks for WeightWatchers, which lost a quarter of its value in a day on news that its leading patron is quitting the board and giving away her remaining stock to charity. Clearly the “Oprah Effect” has lost none of its power to move markets, says Business Insider. When Oprah Winfrey paid $43m for a 10% stake in WeightWatchers in 2015, it
