Yahoo Inc. rose the most since May after it was named a “top pick” by Bear Stearns & Co., which said shares of the most-visited U.S. Web site may rise on speculation it will be acquired by companies such as Microsoft Corp.

Microsoft, the world’s biggest software company, may be willing to offer as much as $40 a share, 76 percent above Yahoo’s last closing price on Aug. 31, based on acquisition prices for other technology companies, analyst Robert Peck wrote in a note.

“Yahoo remains an attractive acquisition candidate for either traditional media companies seeking to deepen their exposure to the Internet or from technology companies like Microsoft,” the New York-based analyst wrote.

Peck, the third-ranked analyst on Internet companies according to Institutional Investor magazine’s 2006 survey, maintained his “outperform” rating on Yahoo stock and his share-price forecast of $30 for the end of 2008.

The shares of the Sunnyvale, California-based company jumped the most in 4 1/2 years on May 4 after the New York Post said Microsoft wants to buy Yahoo.

Yahoo spokeswoman Marissa Coughlin and Microsoft spokeswoman Dawn Beauparlant both said the companies don’t discuss market speculation.

Yahoo also may enter partnerships with other companies, Peck wrote, citing a June 20 report by the Times of London that News Corp., run by Rupert Murdoch, discussed trading its social- networking Web site MySpace for a 25 percent stake in Yahoo.

The expected initial public offering of Alibaba.com Corp., the operator of Yahoo’s Web site in China, may also boost Yahoo earnings by 78 cents a share, Peck wrote. Yahoo has a 40 percent stake in Alibaba, which is based in Hangzhou in eastern China.

Alibaba is seeking to sell shares in its wholesale e- commerce unit, Porter Erisman, a spokesman for Alibaba, said on July 30. The listing may fetch as much as $1 billion this year, people familiar with the plan said in April. Alibaba hired Goldman Sachs Group Inc. and Morgan Stanley for the listing.

Microsoft Chief Executive Officer Steve Ballmer said Aug. 20 that Yahoo would be “an expensive acquisition for anyone to do.” Ballmer, questioned by Charlie Rose at an event in New York, said Microsoft already works with Yahoo and would look for more ways to collaborate.