What is the evidence that Soy is bad?

You certainly came down heavy on soy. Being a long time tofu consumer, I'd be very interested in how soy is bad. What ill effects does it have on the body? What are some of the symptoms caused by ODing on soy? What are your sources of information, etc? I did a quick search on the net, and didn't really find any conclusive evidence. There was some talk about Asians having a greater incidence of thyroid problems, etc., but the conclusions seemed more speculative than substantial. Your help in this matter would be much appreciated. Thanks.