Yes. For a while, you could buy beta-phenyl-GABA in a mass-market grocery store here, right off the shelf. It sounds relatively harmless, but beta-phenyl-GABA is a flat-out synthetic GABA-B agonist [1] developed in Russia in the 1960s. It works similarly to the prescription drug Baclofen. It can cause physical dependence, and has a potentially-life-threatening withdrawal syndrome similar to that of alcohol or benzodiazepines.

When it comes to things labelled as "dietary supplements" in the US, the FDA is more-or-less asleep at the wheel IMO.

[1] Edit: I'm wrong, it's apparently a https://en.wikipedia.org/wiki/Gabapentinoid like gabapentin and the DEA Schedule V drug pregabalin.

Maybe not as high as 2000% but it is very common to see daily multi-vitamins contain doses well above 100% for individual vitamins. The explanation I've seen before stated that these vitamins are water soluble as opposed to fat soluble. You pee so much of them out that these vitamin manufacturers up the amount for better retention. I still fail to see why I would force more into my body than it wants to naturally accept.

The original story mentioned drinking 5-hour energy drinks, or their generic equivalent. Take a look at the nutrition label. 2000% B6 and over 8000% B12!

http://www.energytin.com/blog/wp-content/uploads/2011/12/ing...

Percent dosages vary a lot. I had a B-complex pack once that had as low as 20% of a daily dose of one compound and 2,000% of another.

The supplement industry in the US is completely unregulated and very predatory.