A kind word from Oprah Winfrey temporarily brought the Internet's fastest-growing company ever to its knees on Friday morning.The talk show demigod mentioned Groupon on her show this morning, specifically touting its current partnership with Kiva, a microfinancing company that offers small loans to low-income entrepreneurs around the world. She chose Kiva as one of her "Favorite Things" of 2010, and mentioned that $10 buys a $25 Kiva loan right now.This, apparently, was too much for Groupon to bear.Read More... More on Oprah