Hugh Downs, one of the longest-running hosts of the Today show and 20/20, died Wednesday night at home in Scottsdale, Arizona. He was 99. For many years, he held the Guinness World Record for most hours spent on network television, and he titled his 1986 memoir On Camera: My 10,000 Hours on Television. He first hit a breakthrough in his onscreen career when his co-host on The Tonight Show stormed off in protest of NBC removing a joke from the script. Downs carried the show for more than three weeks alone. Before television, he worked as a radio host.