I found this pie chart that shows a breakdown of the main tweets on Twitter. http://www.google.com/imgres?q=examples+of+information+design&um=1&hl=en...

Given this image, it is appropriate to discuss labeling. This image has third-generation labeling, which means there is a code. One must look to the legend to find what each "slice" represents. The text also mentions the "law of proximity". Although this image doesn't use first-generation labeling, the explanations are not far from the chart. You do not have to flip any pages to understand this diagram. Although, I think it would be more beneficial to have the percentages on the diagram. Some of the slices were close in size, which makes it difficult to distinguish between them.

On another note, this image also displays color constraints. This chart violates a few of the rules regarding color codes. The Twitter logo is blue, so it only makes sense to use colors that are shades of blue, green, and purple. However, according to the text, human beings are only capable of remembering from five to seven different colors. These colors are so close to each other that it will be difficult to remember the statistics, making this diagram ineffective. To be the most effective, the colors used need to be clearly distinguishable and universally used. I don't know about you, but I cannot even figure out the color of the second smallest piece. Maybe a teal perhaps. Last comment, I also had a hard time matching the slice with the appropriate statistic due to the colors being so similar.