United States Justice Department prosecutors are looking into whether Google has been implicit in accepting advertising business from illegal drug sellers. From the Wall Street Journal:
Federal prosecutors have been looking into whether Google employees knowingly accepted business from illegal drug sellers which, legal experts say, could open it up to allegations that it aided illegal online activity.
From the same article:
"On the basis of our analysis, I think they were turning a blind-eye," said Bryan Liang, a California Western School of Law professor who published a 2009 report that found Google and others were profiting from online ads paid for by illegal drug sellers. "They were making a lot of money on this."