Warren Buffett's message to investors: Be careful

Warren Buffett's close followers say he's worried.Bloomberg/Getty ImagesWarren Buffett warned about gambling in markets and the costly AI buildout in a rare interview.Several close followers said he seemed concerned about speculation and overinvestment.Buffett invested last year in Alphabet, now a nearly $31 billion holding for Berkshire.Warren Buffett is worried.The legendary investor called out reckless speculation in markets and the massive cost of the AI buildout during a rare interview