1. Oracle Buys Peoplesoft

Sale Price: $10.3 billion
Year: 2004

In a near hostile takeover that took a year and a half to pull off, the venerable systems tycoons at Oracle wrested control of the immensely popular web-based human resources software outfit, PeopleSoft. All told, the endeavor cost a cool $10.3 billion. Larry Ellison, Oracle's resident yacht aficionado and CEO, likely didn't lose too much sleep over it, though: the hefty sum is just a little more than a third of his own personal net worth.