Fisher Investments dominates more than a quarter of the $22 billion market in ETNs. : (Bloomberg) -- Billionaire Ken Fisher made his name and fortune picking stocks. But over the years he’s also become a huge player in an arcane -- and controversial -- corner of Wall Street: exchange-traded notes. With little fanfare, his Fisher Investments has come to dominate more than a quarter of the $22 billion market in ETNs, whose outsize risks and hefty costs have drawn scrutiny from federal regulators.