Spielberg was depressed over spoilers
Poor Steven Spielberg. He was totally bummed out when all the 'Indiana Jones and the Kingdom of the Crystal Skull' spoilers started filling the internet, scared it wouldn't make the $400 million it needs to make him some money -- the man is worth an estimated $2.7 billion. Luckily George Lucas was there to assure him people would still want to see the movie for Spielberg's interpretation.
It seems like in every other interview with Spielberg and Lucas, there are some words about how irritated Spielberg was about the spoilers. I still have no idea why he cares this much about some people reading some spoilers on the net. I'm sure not even 1% of his audience read it, let alone withhold them from seeing the movie. Or is it because there's just not much else to talk about?
Bias has been added. There is no longer an open mind to fill with your story. Those parts of the story that had been revealed could have been revealed out of context. People like to tell their own stories. Film makers are story tellers.