You know, I was thinking about why they did it that way and had Harry and Cedric touch it at the same time... I think it's to emphasize Harry's guilt. In a sense, it was his fault. Cedric wanted Harry to take it fair and square. But Harry, being the noble sort, was willing to declare it a tie. And that's what got Cedric killed. Of course the only person really responsible is Voldemort, but I'm sure Harry will feel like it was his fault forever.