Both Timberlake and Diaz (at an L.A. Lakers game in 2003) share a history of serious relationships: He spent three years romancing Britney Spears, while she dated Matt Dillon and Jared Leto for years at a time. For Timberlake, the key to longevity is communication. "If you didn't communicate with that person from the very beginning, they can't trust you," he says.