News reports are circulating about dangerous fake drugs manufactured around the world and then sold in bulk to small businesses in the US. Those businesses then sell the drugs to consumers over eBay and through various small business websites.
Diet pills are poorly-regulated and popular, and a common target of scammers. With increasing demand for painkillers sold online, it is likely they are a target for fakes as well.
Investigators imprisoned one Chinese man who was selling potentially deadly sibutramine, a prescription drug linked to heart attacks and strokes, in packages designed to be indistinguishable from the real diet pills. Several people suffered serious problems after taking the pills. In another case, Turkish suppliers were caught selling fake cancer drugs into the US online markets.
The fakes are packaged exactly like the originals, so authorities say there is really no way for the consumer to know if the product they are buying is fake or real, dangerous or not. This is a complicated issue that will take some work to figure out.