In 2007, Valve published a technique to render vector textures at a higher quality than previously possible. The same technique was later used in other engines to improve text rendering based on font textures.
The video you see here was done in Cinder and took only an evening of coding. The font texture was created using a tool developed by 'lonesock' and published on gamedev.net. A simple thresholding shader then performs the 'magic'. Even though each character of the font is no bigger than 50 pixels, the text stays sharp even when rendered at a large scale.
Code for the shader, as well as a sample application, can be found on the Cinder forums:
http://forum.libcinder.org/#Topic/23286000001127007
Links:
Valve's original article:
http://www.valvesoftware.com/publications/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf
Lonesock's font tool:
http://www.gamedev.net/topic/491938-signed-distance-bitmap-font-tool/
Cinder:
http://libcinder.org/
All rendering in this video is done in real-time at 1280x720 pixels. The video may show encoding artifacts - the edges of fonts in OpenGL are usually crispier.