An anonymous reader shares a report: Elon Musk is a man of many characteristics, one of which apparently is not shying away from calling out big names when they are not informed about a subject. A day after Facebook founder and CEO Mark Zuckerberg said Musk's doomsday prediction of AI is "irresponsible," the Tesla, SpaceX, and SolarCity founder returned the favour by calling Zuckerberg's understanding of AI "limited." Responding to a tweet Tuesday, which talked about Zuckerberg's remarks on the matter, Musk said he has spoken to the Facebook CEO about it, and reached the conclusion that his "understanding of the subject is limited." Even as AI remains in its nascent stage -- recent acquisitions suggest that most companies only started looking at AI-focused startups five years ago -- major companies are aggressively placing big bets on it. Companies are increasingly exploring opportunities to use machine learning and other AI components to improve their products and services and push things forward. But as AI is seeing tremendous attention, some, including people like Musk worry that we need to regulate these efforts as they could pose a "fundamental risk to the existence of human civilisation." At the National Governors Association summer meeting earlier this month in the US, Musk added, "I have exposure to the very cutting edge AI, and I think people should be really concerned about it. I keep sounding the alarm bell, but until people see robots going down the street killing people, they don't know how to react, because it seems so ethereal." Over the weekend, during Zuckerberg's Facebook Live session, a user asked what he thought of Musk's remarks. "I have pretty strong opinions on this. I am optimistic," Zuckerberg said. "And I think people who are naysayers and try to drum up these doomsday scenarios -- I just, I don't understand it. It's really negative and in some ways I actually think it is pretty irresponsible."