I am sad to see this man pass on. One of the few actors out there I still enjoyed watching on the screen.
I don't think he had a drug problem honestly, this seems like a suicide to me, intentional and done on purpose. Yes the media invades a lot of actors lives but he was one of the few to keep to himself and stayed out of the light. He went after roles that grew him as an actor. From the wikipedia article on The Dark Knight:
"The challenge of the role put a strain on Ledger's sleep patterns, finding himself unable to rest for more than a few hours each night.
[9]"
Couple this with the divorce from this wife last year and a possible long history of suicidal thoughts (we will never know) and the ability act on those thoughts may have finally come to the surface. I really hope that the media does not spin this as a drug addiction death but rather a suicide of a tormented person. Not pretty anyway but they shouldn't tarnish his image, that is not the proper thing to do.