In response to the Rabbit controversy in 19th century Paris, McDonald's has also had its share of rumors related to the food being served under the golden arches. I remember the kangaroo meat theory of the early 90's, but upon further investigation of the topic, it seems McDonald's has been accused of using many meat products, including worm meat and cow eyeballs. The worm meat accusation was discredited due to the economics of the situation; worms are actually more expensive than beef by weight. Similarly kangaroo meat was seen as unreasonable. In fact, kangaroo meat is more expensive even in Australia once processed. Kangaroo is also more nutritious and reserved for more expensive restaurants.
In the UK a seven year court case showed that among a list of accusations of McDonald's restaurants, it was found that McDonald's is only guilty of mistreating its employees and serving food which leads to heart disease. This isn't a secluded case though, most major corporations face constant lawsuits. With current nutritional guidelines and information posted on every item commercially sold, these accusations are quickly beginning to lose their credibility. I agree with the idea of having knowledge of the food you are being served, but at the same time I see most of these lawsuits as an attempt by an individual to collect from a large corporation.