My answer would be that I don't know - I don't use much soya products (there's no need to do that either, so I don't think I ever will)...
Due to some silly reason our search engine doesn't deal with three character (or shorter) words, so you won't find much if you search for soy. But if you search for soya, you'll find some discussions which may interest you - eg. this one:
Airalien, some soy cultivation involves deforestation in the Amazon rainforest http://www.bloomberg.com/news/2011-0...azil-says.html However some food-grade soy is grown in other parts of the world. Also, the vast majority of the soy grown in Brazil is fed to cattle, not vegans.
It depends on if you're allergic to it, how it's prepared, and a number of other factors.
Generally speaking, it's good for people because it contains pretty high quality protein and fiber, and the lipids have a pretty reasonable fatty acid profile too from what I recall (not great, but not bad either).
As a rule of thumb, though, some diversity in diet is good. Not animal products, but different kinds of plants- there are many types of great beans and nuts to mix it up with.
I have found no compelling reason to avoid any soy products, even un-fermented ones. In regards to fermented soy (as in miso) I can only say there is overwhelming reason to believe it is extremely healthy.
Please bear in mind that there are a number of powerful institutions who have a lot to gain if everything connected with soy (as food for people) is perceived as unhealthy and/or bad for the environment, and those are typically institutions that are not exactly known for their truthful marketing activities (e.g. the meat, milk and dairy producers).
If the articles, opinions, stories etc. you come across that warn of soy cite as sources either the Weston A. Price Foundation or Lierre Keith, then you know for sure that it is simply scaremongering tactics of anti-vegan activists and based on flawed data. Can't really say it more open.
I agree with HRchannel, moderation is the key. After eliminating dairy products from my diet, I replaced milk in my cereal with soy milk. Then I start hearing of the "negative" effects of a soy based diet. The two main arguments were that unfermented soy contained both toxins and an estrogen mimicking hormone. True that Japanese are generally healthier, although soy/tofu I don't believe was part of their diet hundreds of years ago as it is today. I don't believe that long-term soy based diets have been analyzed in recent times although I may certainly be wrong.
That being said, I decided to limit my soy milk to my small bowl of cereal in the morning, and that's about it. Instead of replacing all the dairy I previously ate with soy based products, I simply eliminated them. Instead of drinking a glass of milk/soy milk...I drink water. The pounds dropped just dropped off.
I also found coconut milk based ice cream...dairy free and soy free. so that is a nice treat sometime. Soon I will be trying out almond and rice milk.
I'm certainly not against soy or soy milk, I am personally going to limit my consumption of it just in case. I'm trying not to overdue anything like I used to with dairy milk and cheese.