Ok here is an interesting story from a personal perspective.
FYI I think its crap that Vietnam is trying to sue the company over something used during wartime by the Government.
The active agent in Agent Orange a defoliant was called 2,4,5 T and was produced by Monsanto in Nitro WV during Vietnam. My Grandfather, and my great uncle both worked in the chemical unit that produced this chemical. I think about 40 people or so worked in this unit during that time, but I may be wrong.
Back during the 60's there was not the knowledge about chemicals we have today, let alone the regulations and worker exposure limits. So basically if you worked in that unit, you came into contact with it frequently and in large quantities.
Almost every man who worked in that unit died of some form of lung cancer or skin cancer, including my grandfather. Only two men didn't die of some form of cancer, and both were survivors of cancer. One of them was my great uncle. They sued Monsanto in a class action lawsuit back in the 80's when I was a kid, but most of the people were dismissed from the case because of some legal statue of limitations (ie they were already dead and had been dead for a number of years). But the two survivors won the court case.
So do I think Agent Orange was dangerous and nast? Hell yah. But what concentration and what exposure does it take to effect you is a matter of great debate.