That is a very clever visualization of a 4D data set. I really liked the concept of Swivel.com when it released, but gapminder + google seems like tough competition.
The implementation here is really the amazing part; the basic data-vis tool is pretty simple (I wrote a much uglier variant in Mathematica, inspired by a proprietary stats app), but if they can/will expose this via a clean, open API, then this sort of visualization can become much more widespread. I don't know if/how google intends to make money from this, but if it's available as essentially a commodity visualization component for the web, then everyone benefits.
very interesting. This might be the first time Google ended up acquiring someone based on their Google TechTalk.