Tesla Stock Plunges Following Elon Musk’s Twitter Saga Tesla shares dropped 8.9 percent Friday, the most in two years. Shares are down more than 14 percent since Musk tweeted about plans to take the company private. Musk told 'The New York Times' that no one saw or reviewed his tweet before he posted it. The billionaire frequently teared up during the interview as he discussed the personal strain of leading the electric-car maker. He also detailed his frequent use of the sleep-aid Ambien. Rather than put him to sleep, the drug has sometimes led Musk to spend his nights on Twitter, worrying some board members. Musk has agreed not to tweet again on the possible privatization without first discussing it with the board.