The FDA has issued a proposed mandate that represents the greatest threat to dietary supplements since 1994. Back in the early 1990s, consumers were so alarmed by FDA bullying that they staged a massive revolt. The result was that Congress passed a law prohibiting the FDA from banning popular nutrients (as the agency had threatened to do).
There was, however, a loophole in the 1994 law. The FDA was given authority to regulate ingredients introduced after October 15, 1994.
It has been 17 years, but the FDA just issued draconian proposals as to how it intends to regulate what it now calls "new dietary ingredients". You can find the FDA Draft Guidance on New Dietary Ingredients (NDI's) here. If implemented, some of the most effective nutrients you are taking will be removed from the market. This includes many fish oil formulas and natural plant extracts. A detailed analysis of the FDA Draft Guidance is available here.