Wow, some of you people need to calm down.
1. You don't need credentials to be knowledgeable in health care. Mothers knew chicken soup was good for the flu. Mothers knew greener vegetables were healthier. The Chinese have used ginger for centuries to help reduce the risk of heart disease. All these people knew these things were true long before some dude with a degree declared it true. The list goes on and on.
2. Having the FDA is better than not having one, but let's not pretend that only FDA drugs are safe and useful. There are some drugs used overseas that are great, but they are stuck in FDA limbo. Then, there are drugs that have been approved by the FDA, but they were later found harmful. Looking at you Vioxx.
3. I don't like scammers and cheats, but at least these snake oil salesmen are not outright stealing from you. You can still say no. If anything, I feel bad for them because they have to do this to make a living. That being said, some people actually believe in the benefits of what they are selling. A lot of people are into herbal medicines, and there have been lots of good results from herbal medicines. There is an entire branch of Traditional Chinese Medicine dedicated to herbal healthcare. It won't cure cancer or fix a broken leg, but it might be a healthier lifestyle.