When demonstrating Parallel Sets^(ref) to guests and visitors, I often use the Titanic data set, because people can relate to it and it is entirely categorical. I like pointing out interesting facts the visualization shows (like that the second class was smaller than the first class), but it's really just a collection of numbers to show what the visualization can do. Some of the people I have shown this to feel different about it, though.

A discussion at a seminar in Dagstuhl (Germany) on Information Visualization has led to an interesting insight: what if we completely misunderstood who the users are for visualization? Especially in light of the current developments for broadly usable visualization, we need to rethink the types and levels of expertise that we can expect.