As Elon Musk promises "full self-driving," experts worry Tesla is "using consumers as guinea pigs"

Tesla's cars will in August suddenly activate "full self-driving features," the company's chief executive Elon Musk tweeted on Sunday, three days after federal investigators said a Tesla SUV driving semi-autonomously had accelerated over 70 mph and smashed into a highway barrier. Musk's promotion to his millions of followers -- that the fantastic future of self-driving cars might only be a few months away -- appeared to give the company a leg-up in the auto industry's most competitive technological race. Tesla's stock price jumped Monday by more than 4.5 percent. A Tesla spokesperson on Monday said the cars would only start offering a limited number of as-yet-undisclosed features, not full autonomy itself. But safety experts worried the grand promises of full self-driving capabilities could lull drivers into a false sense of security for technologies that are still largely unproven on the road.