Oprah Winfrey announced on Monday morning that she had agreed to purchase a 10% stake in Weight Watchers International and had signed a collaboration deal to promote the diet company and its services. The announcement has caused shares of Weight Watchers to soar. With the stock changing hands for around $18, Oprah Winfrey has single-handedly generated $700 million in stock market value in two days, given that the company has 63.6 million shares outstanding following the Winfrey deal.