Why would you want to make the base font smaller that the default 16px in the first place? Younger Web Designers with better eyes can read 14px and smaller with ease. This smaller size allows for more flexibility in the font hierarchy also. Most modern browsers allow page zooming. That allows people like me who need glasses to read to magnify the page if I forget my specs and I deperately want to read the latest article on Smashing Magazine. Anyone who regulary needs to use page zooming should upgrade to a modern browser that incorprates this super-useful feature. If not, you could argue that they are not taking enough resposibility for their on-line experience.
A paragraph within a list.
The type in this this paragraph is 16px high. This is the default size most browser manufacturers have decided to implement. Maybe their engeneers are an older demographic. It makes sense.