I recently discovered this website through a friend of mine and thought it was a great example of the problems with machine translations.
The concept is the same as the children’s game “telephone.” In that game a group of children sit in a circle and one child whispers something into the ear of the person on their left, who then whispers what they heard into the person on their left. This continues until the message gets back to the original child. The message that the first kid gets back is usually much different than the one he first sent.
This website runs whatever text you enter through a series of different language translators and then back into English. Like in the children’s game the message is almost always different – and frequently quite opposite.
Check it out yourself: http://www.translation-telephone.com/. My personal favourite is “make love not war;” you get back “We love war.”