t's been three years since Google's historic IPO, and the Mountain View search giant has an anniversary present for its founders: Not only did Larry Page and Sergey Brin beat Bill Gates in developing a better search engine, the young technologists also can boast of bringing shareholders a bigger reward.

Since Google went public Aug. 19, 2004, at $85 a share, its market value has grown nearly 500 percent to $156 billion. In comparison, Microsoft's value had not quite quadrupled on its third anniversary way back in March 1989.

But Google's precocious performance has come at a price: Antitrust regulators in the United States are probing its proposed $3.1 billion purchase of DoubleClick, an Internet advertising company, and European regulators are poised to follow suit. Meanwhile, open-source activists are developing alternatives to Google's popular search engine.