Don't forget the outbreak of gastroentritis caused by Cryptosporidium in Milwaulke a few years ago--that one sickened a few hundred thousand people. If Cryptosporidium was a little more amicable to genetic engineering, just splice in an Antrax toxin gene or one for botox, and you'd have one of the worst catastrophes imaginable. That may be out of reach for people like alQ, but it's illustrative of how easy it would be to cause massive problems through food & water supplies.