According to the promotional copy:
"The words we suggest," says senior editor Steven Kleinedler, "are not meant to be exhaustive but are a benchmark against which graduates and their parents can measure themselves. If you are able to use these words correctly, you are likely to have a superior command of the language."
I’m pleased that I know most of them. Though I would use only a fraction in my day to day vocabulary.
Also, I think the key word in the title is SHOULD. I’m sure testing a random sampling of people on the streets of any western, English-speaking, city would be discouraging if we used this list as a benchmark.
Update: A hat-tip to the good folk over at the CommonCraft blog for the link.