|“||t's sort of like he has a license to kill with impunity, to wreak havoc without any consequences||”|
—Frank Hole, whose 17-year-old daughter, Leta, died in 2002 after taking an intentional overdose of Cahill's weight-loss pills that actually contained a highly toxic chemical pesticide banned for human use
Matt Cahill sells highly dangerous substances as "dietary supplements." Cahill operates from the USA but people from other nations can buy his products online.
Cahill spent two years in prison for killing one of his
victims "patients" with a mixture of baking powder and pesticide. He is now out and making $30,000.00 a month selling harmful valuable herbal supplements. PZ is strongly critical. 
After a 15-year old was found unconscious, it was discovered they were taking a Cahill product marketed as "all-natural" which contained amphetamine-like compounds.
And, of course...Edit
Mr. Cahill does not have any medical license, board certification, nor certification in any medical field. By his own admission, he does not even have a bachelor's degree.
Adapted from RationalWiki where I wrote part