Then I had an idea...
Wikipedia:Infobox where the data lives in wikipedia. sparql, anyone? or grddl?my bookmarks, 2006-02-16
The next day, in the SemWeb IG meeting, I met Markus Krötzsch and at lunch I learned he's working on Semantic MediaWiki, a project to do just what I'm hoping for. From our discussion, I think this could work out really well.
For reference, he's 3rd from the left in a photo from wikimania 2005.
I use wikipedia quite regularly to look up airport codes, latitutes, longitudes, lists of postal codes, and the like; boy would I love to have it all in RDF... maybe using GRDDL on the individual pages, maybe a SPARQL interface from their DB... maybe both.