Like everyone else who's tried it, I was completely charmed by World of Goo, finishing it in about a week. What surprised me about it was that it seemed familiar: although I don't know if this was their inspiration at all, WoG's gamemplay is basically a force-directed node graph, plus gravity and very clever level design.
The term "force-directed node graph" is kind of wonky. You probably know it better from Visual Thesaurus, or the 6pli del.icio.us tag browser. It's a method of taking a semantic web of interconnected nodes, then allowing it to self-organize (instead of placing the nodes manually) by A) making them repel each other while B) applying elastic limits to the connections between them. It is a lot of fun to mess with. I could drag nodes in one of these graphs all day long, watching them spasm and then reassemble themselves into a kind of order.
I don't know that World of Goo takes its inspiration from these kinds of node graphs--the idea isn't exactly revolutionary--but I certainly think that the simple enjoyment of adding nodes and watching them shift in response is a part of the game's appeal. It's got me thinking about other simple pleasures, and wondering if they, too, could be made into games: stuff like throwing a cursor across screens with a trackball, zooming in and out of Google maps, or playing with the 3D formula graphing on my old TI calculator. It's the kind of thing that's mindlessly rewarding, and that data visualizations are increasingly good at creating.
Which raises a second question: as we're increasingly confronted with data, how will visualization crossbreed with gaming, so that either the games become more reactive, or the graphs become more entertaining? How does it change our relationship with data--and what that data represents--when it's primarily presented to us through software toys?