"The Incredible Shrinking Cereal Box"

The idea behind this article from CNN/Money is that rather than raise prices, food companies are opting to put less in the box. The article presents it as some kind of underhanded theft, but I'm not convinced it's a bad trend. From what I've read, people tend to eat and be satisfied with what is placed before them (to an extent of course). So if food comes in lower quantities, could this help fight obesity? Just a thought.