Money is flowing into activist hedge funds at a quickening pace and the managers of those funds now rank among the most important drivers of auctions, mergers and acquisitions. Companies from Apple and eBay to PepsiCo and Abercrombie & Fitch have been targeted by investors unhappy with the course set by boards and top executives. But who are the most successful activists right now? And which ones are having a tough year? Probably not who you think.