Has Internet mania turned to Internet lunacy? Since June 10, shares of Yahoo!, the Web's leading portal company, have rocketed 29% to a lofty 148 1/16 on June 23. Yahoo!'s recent lift stems from new deals between NBC and Disney and Yahoo! rivals Snap! and InfoSeek. Such interest from major media companies is fueling rumors of more deals to come. With a nearly $7 billion valuation, Yahoo! now trades at 33 times revenue compared with America Online, which trades at less than six times revenue.