The guy who practically invented tech journalism for non-geeks has retired. Walt Mossberg has penned his last column. His parting thought: We’re in a period of tech stagnation right now, but we’ll soon undergo an “ambient computing” revolution that’s going to stick computers and sensors in just about everything — and raise some really uncomfortable questions about privacy and hacking. “If the FBI can threaten a huge company like Apple over an iPhone passcode, what are your odds of protecting your future tech-dependent environment from government intrusion? If British hospitals have to shut down due to a ransomware attack, can online crooks lock you out of your house, office, or car?”