I stumbled across a very interesting article on digg.com - that highlights one of the questions on McDonalds' Make up your own mind website. For those of you who dislike clicking through links to find the information, have a look at this:
It's hilarious that McDonalds has this FAQ on their site - and they've answered it! It's put me off milkshakes from there now, but I'll probably forget about it in the near future, as after all - it's an urban myth according to them.If you want to see it for yourself, visit their Make up your own mind site and search for milkshake - it's near the bottom.