If I were them, I'd go for the mall of America. I'm not them, and therefore I hope that there are systems to stop a biological attack in one of the the most populated indoor spaces in the USA. Domed stadiums and larger office buildings should be watched too. Also, if Iraq is involved in this anthrax thing, we MUST use a nuke on them. It can be a small tactical instead of a large ballistic missile MIRV, but we must use nuclear weapons if a foreign nation is involved in order to make the successful 50 year old idea of deterrence work in the future. This would be completely legal by international law and all treaties.
Also, the anthrax is obviously small enough not to get stuck before it reaches the lungs. They just seem to not want to admit that it is weapons grade. They have also made stupid statements about how a crop duster could not be used to spread anthrax because a complicated mechanism would need to be invented to spray a powder. I guess it'd be too hard for a terrorist to go to a hardware store, buy a sandblaster, and adapt it to the cropduster. I swear the goverment must think the terrorists are retarded. Either that, or our govt's biowarfare experts are retarded.