Rick - Great post! I was at a round table at USCOTS 2013 talking about incorporating 'Big Data' into the discussion in elementary stats courses and your example here is a great work-around for an issue that I have seen with scatterplots of huge datasets. Imagine you are plotting 10,000 datapoints and 9750 of them are the same few values while the other 250 are scattered in a way that makes a casual observer 'think' there is a trend. But if we shift over to this kind of visual we won't make the mistake of believing there is a trend based on a relatively small number of points.