For me, BHT is on my "avoid it if I can" list. It's an unnatural chemical, so there is no way it is good for you, but I also don't think I will drop dead from eating a box of corn flakes. If I have a choice, I will go for the non BHT product, but sometimes I cannot avoid it and don't really stress over it.
I read that it is a banned substance in England, and that some studies have shown negative side effects when taken in large doses. How much BHT ends up inside you from the packaging is debatable (and probably how the corporations got the FDA to approve it in America).
A bigger issue for me is the simple fact that BHT is completely unncessary. If your corn flakes did not have BHT, they *might* not taste fresh if you opened the box in 5 years.... I think the real issue is that companies can save money on crappy packaging by using the BHT to compensate. Just another example of the corporate world saving a few cents off the backs of our health, while the government turns a blind eye.