According to the BBC, food packagers are making stated portion sizes on the "Nutritional Information" panel too small to make it look like their foods aren't as fatty and salty as they really are. The example they gave was a stated portion size of one 15g chicken nugget.
I don't eat chicken nuggets often, but my real problem with this is cereal. Yes, maybe I do eat a bit too much sometimes, but I figure a decent amount of cereal to eat for breakfast (when I have it) is a decent-sized bowlful, which is also about enough that I can work until lunchtime without getting all hypoglycemic all over the place. I don't usually buy cereal in the holidays, and the other day I remembered why. A friend had asked me to finish up some milk for them, so I bought a box of Jordan's. Really nice, but the boxes only seem to hold 3 bowls of cereal each. That means that if a family of 4 were eating it, you'd average over 9 boxes a week, at a cost of nearly £30. For breakfast cereal. It's nice, but it's not that nice.