LIKE EVERY would-be entrepreneur, Nick Denton had an idea that kept him up late at night. Finally, tired of the usual 9-to-5, Denton quit his job two years ago and followed the herds into cyberspace. At 33, he's not looking back. "I only wish I had done this sooner, says Denton, an affable Brit. Of course he does. By the time you read this, Denton expects to have sold another chunk of his San...