It looks as though the mystery of the Anthrax attacks that followed the World Trade Center attacks may have been sold, with a man the FBI were preparing to charge committing suicide. Given the centrality of the unsolved Anthax mailings to conspiracy theorists* it is unsurprising that a lot of forums are speculating that he was bumped off by the US government to keep him quiet.
Personally I think that Barry George was behind the anthrax. Unlikely you say? There is about as much evidence for my theory as there is for any of the other conspiracy theories so I don't see why he can't be blamed.
The most widespread conspiracy theory is roughly that someone inside the government mailed Anthrax to individuals including Democratic Senators Tom Daschle and Pat Leahy in order to push through the dreaded Patriot Act. Exactly how bolstering the anti terror credentials of two of the leading opponents of the Act (at that time) was supposed to help them isn't clear.
Over at the Belmont Club blog, Richard Fernandez has more on the subject.