It used to be only the designiest of sites (graphic design sites, artists sites, and high-end architectural sites) that would use big contrasts in font sizes. Now even average sites are starting to widen the gap between biggest and smallest text used on the page. The large text catches your eye and makes for a more dynamic page when used with smaller text because it creates more hierarchy and makes it easy to navigate through the information.

Check out the contrasts in the examples below