Billionaire Larry Ellison more than tripled the amount of Oracle Corp. stock he has pledged against lines of credit in the last year, effectively reducing his fortune by billions of dollars. Ellison owns 1.1 billion shares of the Redwood City, California-based software maker. According to the company's proxy statement, which was filed with the U.S. Securities & Exchange Commission on Sept. 21, 139 million shares are "pledged as collateral to secure certain personal indebtedness, including various lines of credit." The collateralized stock is valued at $4.5 billion.