Heath Ledger was found dead only a few hours ago, and almost immediately people started hitting the message boards asking how it would affect The Dark Knight's summer release.
That seems wildly selfish, but I have to admit that it was the first thought that crossed my mind as well. I assume his contribution to the film is complete, and I wasn't expecting much from the movie anyway (since I was not impressed with Batman Begins), but I think his tragic death adds a new layer of meaning to the film.
It will be interesting to see how things play out when the movie's released, but I can imagine that his performance will take on an added resonance, much like Brandon Lee's performance seemed enhanced in The Crow by the contextual knowledge of his death. And, obviously, Heath Ledger was a far more highly regarded actor than Brandon Lee ever was.
Celebrity deaths are always bizarre, because it makes you feel like you lost someone you knew. But we didn't know this guy. We just saw him flicker on the screen a few times. What makes him anything other than a stranger? Celebrity is a weird thing.