As soon as I read the Krug quote above, I immediately remembered the line from the movie Superman Returns. It's said when Perry White, the Editor in Chief of the Daily Planet, is explaining to Lois Lane why she must write an article about Superman being back on Earth.
When we initiate our scanning mode in order to learn new information, we only search for the important stuff, like those mentioned above. Krug relates this method to people driving past billboards, because unless you're sitting at a standstill in traffic, you're not going to dissect a billboard's information. So, the easiest way to get people their needed information is to write/design your website for drive-by users! This is one of those times when you've got to go with the ultimate flow.
I have to write though, that I rarely read newspapers when I was younger. I'd occasionally look over my dad's shoulder when he was reading the paper after getting home from work, but I mostly just sought out the comics. However, I quickly found a few magazines that held secrets within their pages and sat down to unconsciously learn the conventions of newsprint. One was actually foreign based and so I had to teach myself to read "backwards" from typical english conventions!
All in all though, Krug's right about people learning how to process print and online news without them even knowing it. Readers now look for differentiating headlines and such now without realizing it. Funny how the world works sometimes.