Interesting--I believe the anthrax was not sent by foreign terror groups for the exact same reason. The letters are too obvious--it's more like a case of misdirection. If you look at what happened, the letters caused a minimal loss of life, and caused a great deal of reaction on our part. We are now better prepared to deal with this type of attack than we were before. When was the last time Al Qaeda put safeguards on its attacks to REDUCE the loss of life? Never. The letters (a) told people it was anthrax, (b) told them what to take (admittedly, not the best choice, but still) (c) were taped to reduce the chance that spores would be released prior to being opened, (d) were folded with a "pharmaceutical fold," also to reduce chance of spores being released. The early warning, the prescriped antidote, and the precautions--none of these are Al Qaeda calling cards. They strike with an attempt to cause the most damage possible. The person who used this anthrax could have killed thousands, but did not. Why?
Remember a Freeper who called himself The Great Satan? He seems to have gotten himself banned. But while he was here he pushed the idea that Bush would never go after Saddam Hussein because we did know where the anthrax came from, and it was him. And the message was, "Come after me, and you get this."
Suppose that guy was right, and we are about to find out where the WMD's went. They're here. And the capture of Saddam Hussein is the event that sets off some doomsday plan he cooked up. He is evil enough to have planned such a thing; he had the money to make it happen; and the Atta Boys would have been happy to serve as the deliverymen.
I hope that's not it.