Although I'm a strong opponent of soy and/or ANY soy by-products, I would think soy nuts once in a while would be fine. Keep it to 1 time a week or less. Consider peanuts/almonds or walnuts - high EFA count and IMO taste better.
Basically, I associate soy w/ estrogen, which no-one needs more of. Why not just go w/ almonds they are a way better source of protein and taste better IMO.
I have not seen one study that proves a direct connection w/ soy and cancer reducation done on humans for a long period of time. The reason the anti-cancer properties are brought it b/c in men high-estrogen lowers testosterone; thus, it would be a "good" thing for anti-cancer (prostate), but low-testosterone, I rather not eat something that will give me low test levels and increase my estrogen.