With Internet stocks soaring, Yahoo cofounder Jerry Yang today became the latest Net executive to gain entry into the billionaire club, joining Yahoo cofounder David Filo and Amazon.com chief executive Jeff Bezos.

Yang hit the milestone with Yahoo's opening price today of 178.875, which was up from Thursday's close of 172.875. Yang, 29, holds 5.7 million shares, or a 12.2 percent stake in the company.

His net worth closely trails that of Filo, 32, who reached billionaire status with Thursday's opening price of 173.50. Filo holds nearly 5.9 million Yahoo shares, or a 12.8 percent stake, according to the company's latest proxy statement.

Yahoo spokeswoman Diane Hunt said that Yang and Filo are private people who do not like discussing their wealth. "It's not important to them," she said. "It's not their focus."

The search engine company's stock has been on a rocket ride since early June, when it traded slightly above 100 a share. Yahoo's stock has been climbing all over itself as it repeatedly has set new 52-week highs recently--with today marking the latest peak for the stock.

Yang and Filo now join the ranks of other recent billionaires, such as Amazon.com CEO Jeff Bezos, 34. The online bookstore founder holds nearly 19.8 million Amazon.com shares--or a 41 percent stake in the company, based on a 2-for-1 stock split last May. Based on Amazon.com's closing price today of $139.5 a share, Bezos is worth nearly $2.8 billion on paper. He first cracked the $1 billion barrier in early June, when Amazon.com shares hit 51.25.

Yang ended the day with paper wealth of $1.14 billion, while Filo's net worth stood at $1.2 billion, based on Yahoo's closing price of $199.25 per share.

Both Amazon and Yahoo were founded in 1994, meaning that the youthful entrepreneurs who built the companies became billionaires within a very short time span. Yahoo hit the public markets in April 1996, while Amazon went public in May of 1997.

The billionaire boys club that Yang, Filo, and Bezos recently joined also includes "old-timers" like Microsoft's cofounder, chairman, and chief executive Bill Gates. His net worth stood at around $50 billion at last count.