Some tech blogs are fueled mostly by snark and rumor. AllThingsD, by contrast, is powered by old-fashioned hard work. A Web-based spin-off of the Wall Street Journal's swanky annual conference, it features Journal tech columnist Walt Mossberg, ace investigative reporter Kara Swisher and a growing lineup of writers who specialize in meaty, dependable coverage of consumer gear, Web trends, mobile communications, business computing and more.