Artificial intelligence will solve Facebook’s most vexing problems, chief executive Mark Zuckerberg insists. He just can’t say when, or how.  The company has said that advances in AI have helped it remove thousands of fake accounts and “find suspicious behaviors,” including during last year’s special Senate race in Alabama, when AI helped spot political spammers from Macedonia, a hotbed of online fraud. Facebook, Zuckerberg said Tuesday, has also been “very successful” at deploying AI to police against terrorist propaganda. “Today, as we sit here, 99 percent of the ISIS and Al Qaida content that we take down on Facebook, our AI systems flag before any human sees it,” he said. (Nonprofit groups like the Counter Extremism Project have argued that Facebook has exaggerated its achievement and failed to crack down on well-known Islamist extremists.)