Cassava (also called yuca and manioc) is definitely poisonous in its raw state. One of the ingenious developments in the history of humans is that so many peoples developed ways to make it edible. Indians in what is now Guyana had four feet long woven baskets into which they would stuff mashed cassava mixed with water. They would pull the baskets from both ends to squeeze the mash dry, thus washing out the cyanide. the result was a food rich in carbohydrates, which was one of their staples.

We eat cassava in a more processed form: tapioca.

Cassava is not the only food that is poisonous in its raw state. Bitter almonds is another example. The toxins are an evolutionary development that protect the plant from insect or animal predation.

The wikipedia writeup on cassava is most likely referring to bitter cassava. I have grown up in Africa and have had cassava as part of my diet all my life. It cooks like a potato. Just peel, wash and either cook it water and little salt on the stove top or pressure cook to 3 whistles; you can then deep fry it for cassava chips

Do you mean yuca (cassava)? When using this, you do need to make sure you soak it at least 18 hours or use one of the other safe processing methods. It contains toxins (a variety of cyanide, I believe) that can make it toxic to humans if you don't cook it properly. Here's more information:
http://en.wikipedia.org/wiki/Cassava

Yucca (native to the Americas & the Caribbean) and taro (native to Southeast Asia) are different, though they're both starchy root vegetables.

All the recipes I've seen for fried yucca call for boiling or steaming first -- it's too dense and fibrous to be cooked through by a fast, high-heat method like frying. But they're well worth the extra step!