I've never know anyone to even get sick off of mushrooms, urban legend mostly.
I heard someone say the same thing about influenza actually killing people. He said that to my face after I asked him if he got his flu shots yet. And then he told me that the flu vaccine kills more people than the flu.
The guy was a plumber.
From the FDA food safety website.
Specific cases of mistaken mushroom identity appears frequently. The Early False Morel Gyromitra esculenta is easily confused with the true Morel Morchella esculenta, and poisonings have occurred after consumption of fresh or cooked Gyromitra. Gyromitra poisonings have also occurred after ingestion of commercially available "morels" contaminated with G. esculenta. The commercial sources for these fungi (which have not yet been successfully cultivated on a large scale) are field collection of wild morels by semiprofessionals.
Cultivated commercial mushrooms of whatever species are almost never implicated in poisoning outbreaks unless there are associated problems such as improper canning (which lead to bacterial food poisoning). A short list of the mushrooms responsible for serious poisonings and the edible mushrooms with which they are confused is presented in Table 3. Producers of mild gastroenteritis are too numerous to list here, but include members of many of the most abundant genera, including Agaricus, Boletus, Lactarius, Russula, Tricholoma, Coprinus, Pluteus, and others.
The Inky Cap Mushroom (Coprinus atrimentarius) is considered both edible and delicious, and only the unwary who consume alcohol after eating this mushroom need be concerned. Some other members of the genus Coprinus (Shaggy Mane, C. comatus; Glistening Inky Cap, C. micaceus, and others) and some of the larger members of the Lepiota family such as the Parasol Mushroom (Leucocoprinus procera) do not contain coprine and do not cause this effect.
The potentially deadly Sorrel Webcap Mushroom (Cortinarius orellanus) is not easily distinguished from nonpoisonous webcaps belonging to the same distinctive genus, and all should be avoided.
Serious mushroom hunters are usually a pretty intelligent group of people. I just wouldn't trust gambling my liver over a lunch.