prostoalex writes "Wall Street Journal profiles one of the Valley's most mysterious and secretive Web companies. A leader in online classifieds space and by some measures one of Web's top sites, CraigsList is ostensibly anti-ad and anti-self-promotion. From the article: "One industry analyst has estimated that Craigslist could generate 20 times that $25 million just by posting a couple of ads on each of its pages. If the estimate is to be believed, that's half a billion dollars a year being left on the table. What kind of company turns up its nose at $500 million?""