Risks: Almost all modern soy (in the US especially) is a GMO product. Soy is very heavily modified and the very make up is no longer natural. It is always a risk to ingest something that is so modified that your body is no longer receiving the good benefits of the food. (Check out the no-gmo movement, if you are unsure what I mean). Soy is VERY high in phytoestrogens. These look and act like the hormone estrogen in your body and interact with the estrogen receptors to have increase the estrogen effect on your system. This is very bad for those of reproductive age (both male and female). Your body is attempting to maintain hormonal homeostasis and, unless you have other health issues, extra "hormone" will be negative for your system.
Benefits: Soy in its ancient and natural state before gmos can help arthrosclerosis. It also acts as a perfect protein (great for vegetarians if you can find the non-gmo version). Soy, because of its phytoestrogens, has also been shown to be a helpful home treatment for post-menopausal symptoms. It also has been shown to decrease polyp size in colon cancer. Research for yourself on pubmed using the keywords "soy benefits and risks". http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0022127/