I know a lot of people are going to say drugs but i don't think that has been proven yet. And i won't believe it until it has. I agree with MadMarcus, shouldn't assume. Don't need to always believe the rumors they say.
It is truly sad that every time a celebrity dies nowadays, the automatic assumption is drugs. Even if the person had a history of drug abuse, it doesn't mean that was the cause of death. Let's concentrate on living and let the dead rest in peace.