Both cosmetics and "dietary supplements" are regulated differently than drugs by the FDA. While FDA requires fairly rigorous pre-market testing for drugs (though maybe not rigorous enough, given some of the recent problems with Vioxx, etc), the FDA has no authority to regulate supplements and cosmetics pre-market unless they make medical claims. They can only pull things off the shelf if they make unproven medical claims, are contaminated/don't follow labeling requirements, or are connected to a large incidence of adverse events (like ephedra was) and therefore can be construed to present a public health risk. Unfortunately this can't be proven until these events are reported in sufficient number to the FDA...

This is a huge loophole that Congress needs to fix in my opinion.

However, I also think we need to take "science" we find on the internet with a grain of salt. I am not a scientist, and some of these claims are pretty extreme, and I can't really evaluate them. History has certainly shown that we sometimes approve dangerous chemicals for public consumption, but there are lots of quacks out there I can't evaluate too...