Mike, Andy doesn't mention anything about Bentonite clay in "Amalgam Illness". I know it's supposed to be wonderful for drawing out toxins and I know a lot of people recommend it.
I do wonder if it can also pull out some nutrient minerals too....I tend to get deficient in potassium quite easily so tend to avoid things like bentonite. I'm sure overall though for a lot of people the benefits outweight the disadvantages. Just one other thing.....it's supposed to contain highish levels of aluminium so it could pose problems if you have high levels of alum in you.