My answer does not require Javascript and only relies on CSS3 (available in most modern browsers). I personally like it very much if design is not relying on Javascript too much.
My answer is a “pure CSS3 , no Javascript required”-solution:
The solution as can be seen here (http://jsfiddle.net/uNF3Z/16/) uses the following additions to the CSS styles (which make use of the @media query of CSS3 which)
@media all and (min-width: 50px) { body { font-size:0.1em; } }
@media all and (min-width: 100px) { body { font-size:0.2em; } }
@media all and (min-width: 200px) { body { font-size:0.4em; } }
@media all and (min-width: 300px) { body { font-size:0.6em; } }
@media all and (min-width: 400px) { body { font-size:0.8em; } }
@media all and (min-width: 500px) { body { font-size:1.0em; } }
@media all and (min-width: 600px) { body { font-size:1.2em; } }
@media all and (min-width: 700px) { body { font-size:1.4em; } }
@media all and (min-width: 800px) { body { font-size:1.6em; } }
@media all and (min-width: 900px) { body { font-size:1.8em; } }
@media all and (min-width: 1000px) { body { font-size:2.0em; } }
@media all and (min-width: 1100px) { body { font-size:2.2em; } }
@media all and (min-width: 1200px) { body { font-size:2.4em; } }
@media all and (min-width: 1300px) { body { font-size:2.6em; } }
@media all and (min-width: 1400px) { body { font-size:2.8em; } }
@media all and (min-width: 1500px) { body { font-size:3.0em; } }
@media all and (min-width: 1500px) { body { font-size:3.2em; } }
@media all and (min-width: 1600px) { body { font-size:3.4em; } }
@media all and (min-width: 1700px) { body { font-size:3.6em; } }
What this in effect causes is that the font-size is adjusted to the available screen width. This adjustment is done in steps of 100px (which is finegrained enough for most purposes) and covers a maximum screen width of 1700px which I reckon to be amply (2013) and can by adding further lines be further improved.
A side benefit is that the adjustment of the font-size is occuring at each resize. This dynamic adjustment (because for instance the browser windows is resized) might not yet be covered by the Javascript based solution.