Widely used herbicide linked to cancer : Nature News & Comment
I dunno - I tend to assume that chemicals that pretty rapidly cause living things to die are probably going to be cancer causing if you're exposed to too much of them.
The issue is more about the dose, really.
And having said that, I still rely on my common sense to tell me that the Monsanto tactic of making Roundup tolerant crops so you can spray heaps of chemicals on them to control weeds is not that great an idea, certainly in the long term, but also quite possibly in the short term.
Update: I probably linked to it before, but here's a short report from the Nature website that explains how herbicide tolerant weeds have developed despite Monsanto's improbable claim that they wouldn't.