"Spam Will Be Solved in Two Years" — Bill Gates (2004)

Bill Gates's 2004 Davos prediction that spam would be eliminated by 2006 ranks as one of tech's most audacious misfires. Twenty years later, spam still accounts for roughly 45% of all email traffic worldwide, a figure that notably outperforms #2's prediction in terms of persistent failure. This stubborn 45% share means nearly half of the 347 billion emails sent daily are unwanted, proving Gates's optimism wildly underestimated the ingenuity of spammers and the complexity of filtering systems.