Gary Price at ResourceShelf noticed that Yahoo registered two trademarks: "Trovetopia" and "THE N9NE," with Trovetopia also being the name of an active Yahoo shopping site.
I'm not sure about THE N9NE, but according to Chris Saito [thanks for the quick response!] Trovetopia turns out to be a "test bed for [Yahoo!] APIs its built entirely using the web services available on the Yahoo! Developer Network.
It's cool to see Yahoo playing around with its own APIs. Yahoo Tech is another place to see the power of the APIs. Considering that I get an email each week about people interested in using a shopping comparison engine API, it's smart to put these services on display.