Not only are many of Groupon's top investors leaving the company due to the share price dropping by three-quarters since its IPO last year, many of the company's senior executives are jumping ship, too, reports Reuters. The latest to leave is Lee Brown, the head of Groupon's national sales. Janya Cooke, one of the company's top sellers, has also left, reports Business Insider. Sales, easy when the company was a hot new thing, have been hit hard since Groupon started to lose its luster. All is not well at Zynga, either... (More Groupon stories.)