Michael Bloomberg is a marked man. Dow Jones, the 110-year-old publisher of business news, has threatened to "get" him. British media conglomerate Reuters recently launched a new product it informally dubbed the "Bloomberg Killer." Bloomberg also ranks No. 1 on the hit list of a powerful new joint venture formed by Salomon Brothers, Morgan Stanley, First Boston, Citibank, Lehman Brothers and Goldman Sachs.
At 5 ft. 10 in., balding and a little paunchy, Bloomberg, 50, is no Arnold Schwarzenegger. But to his competitors, he has seemed like the Wall Street version of the Terminator. With fewer resources and less experience than...