It's been a groundbreaking year for women in business. IBM appointed its first female CEO in Ginni Rometty. Sheryl Sandberg led Facebook through a much-anticipated IPO. Irene Rosenfeld split Kraft into two public companies, and Marissa Mayer jumped from a top Google exec to the CEO seat at Yahoo. See the those named the top businesswomen on the Forbes 2012 list of The World's 100 Most Powerful Women.