This month, city officials in Aliso Viejo, California considered banning Styrofoam cups from city-sponsored events, in part because the manufacturing process involves a dangerous chemical, Dihydrogen Monoxide. It seems that a paralegal working for the city actually took seriously a website claiming what other writeups here do: that Dihydrogen Monoxide is involved in acid rain, cancer, pesticides, and many other objectionable phenomena. City documents stated that foam containers are made from a chemical that could “threaten human health and safety,” and should thus be banned.
The city is still considering banning foam containers, though now simply because they’re a pain to clean up when they break into small pieces.
This story was reported by the Associated Press at <http://customwire.ap.org/dynamic/stories/H/H2O_HOAX/>. More about the Dihydrogen Monoxide issue can be found at <http://snopes.com/toxins/dhmo.htm> and <http://www.dhmo.org/>, and in other Everything2 writeups.