Steve Jobs was a ferociously private person. Secrecy was the default mode for all aspects of his life, at home and with Apple.
Even though it was becoming apparent to observers that he was ill, Apple had a very strict policy of offering no comment on rumors of Jobs's health. That didn't stop the speculation, which grew to a fever pitch in 2008.
He was noticeably thinner at WWDC in June. In July, apparently worried that the New York Times was going to say he had cancer again, he made an off-the-record call to op-ed writer Joe Nocera to chew him out and try to kill the column.
Then on August 27, 2008, Bloomberg News announced that Steve Jobs had passed away.
It was a simple mistake; someone had pushed the publish button on an advance obituary of the sort that most news organizations have at the ready for older famous people.
Jobs had fun with this by starting the keynote with the famous Mark Twain misquote "The reports of my death are greatly exaggerated". It allowed Jobs to address the health rumors without addressing them. He could bat them away with a joke.
But his health continued to worsen as the year went on. He had no choice but to take another major medical leave four months from now.