 In maybe the most famous case, someone impersonated the drug maker Eli Lilly and said that insulin would now be free. The real Eli Lilly's stock price dropped more than 5%. It was a vivid illustration of why companies like Twitter make rules in the first place. Impersonators were suddenly all over the site. And so, okay, we have to ban them. But somebody has to review them. We can't just, like, ban everyone.