It seems to me the government failed to make its case against Army scientist Bruce E. Ivins. As I see it, it was established that Dr. Ivins was a little eccentric; he may have committed burglary of the sorority houses, and he may have stolen some young ladies' underwear. If this indeed happened, Dr. Ivins broke some laws, but in a college prank sort of way. This does not make him a terrorist or a mass-murderer. The government failed to establish conclusively an opportunity, and it sure failed to establish a motive.
Who had both motive and opportunity? Who could access American weapons-grade anthrax, and would have motive to spread it around?
Who would target not just random American people, but specifically certain elements in the media and certain US Senators?
It seems to me the idea was not to maximize casualties among the American people, but rather, to maximize publicity about the potential for casualties. Unlike hoaxes a few years previously, this time the perpetrator did indeed have high-grade anthrax, and wanted to make sure America knew that, but without inflicting actual mass casualties, and while trying to make it look like Al Qaeda may have been responsible.
Who had both motive and opportuntity to do this?