I tested the Labeling based on size code comunity example in order to show labels with the country names based on Countries02.shp file, and it was working on some installations but not in others. Finally I figured out that it was depending on screen resolution, for instance with 1024x768 was not showing the country names until a high zoom is applied, but with higher screen resolutions it works fine showing the name labels according with the country area.
Could you please check it?