According to one leading expert, the Dow could hit 50,000 by 2015 and 100,000 by 2020. Should you buy? Maybe. But then, another expert says the Dow could lose 90 percent of its value and close below 1,000 by year end. Oh my! Should you sell? What's a wise investor to do? A wise investor will ignore this nonsense. Wild market predictions aren't investment advice. They're grandstanding by newsletter writers and investment gurus trying to grab media attention. Sometimes I wonder if the self-proclaimed market experts who make these predictions do double duty as supermarket tabloid headline writers and come...