Most data is ugly. Lots of substance, but no style unless you're a deep math genius who finds rapture in the music of numbers. I'm not one of those guys (although I like them - alot), but I've found that with the proper visuals, I can understand volumes of data that would be dead to me in its original form.
The best data graphics I've ever seen are those produced by Hans Rosling. His 2006 TED talk is well worth its 20 minute duration. With a relatively simple combination of color, size and movement, he animates years of data to reveal startling insights that are not intuitively obvious. Strong visual insights, like those he creates, can even predict what will happen next.
One set of data I'd love to see him model is the movement of 18-29 year olds in the US. Not on a street level basis but in terms of where they choose to live after college. This age group has the greatest freedom to select where they want to live, so their choice most often reflects significant cultural changes. By moving enmasse, they create "hot" cities that have disproportionate influence over the rest of the nation. In the 60's, the "hot" city was San Francisco, spawning and spreading the influence of Hippies. In the 80's, the "hot" city was Seattle, broadcasting the Grunge lifestyle to the rest of the country. In the 90's, both LA and Silicon Valley vied for dominance: LA with its Latino emphasis and SV for dotcom craziness. As LA and the Valley lost heat in the new century, NY and Miami warmed up.
My sense is that both NY and Miami are starting to cool slighly in pop culture terms, and a couple of new "hot" cities are starting to simmer. My money is on either DC or Chicago for one. Other contentors? If you're an 18-29 year old, where would you want to live?