Spotted this on the All Points Blog about Yahoo testing (I was unable to get them) what the author calls "geolinks" for addresses and locations in Yahoo Mail messages.

http://www.allpointsblog.com/archives/2119-guid.html
The post includes a screen cap. I tried to activate the feature using both the Yahoo Mail Beta and the old service using both IE 7 and Firefox 2.0 and came up empty. I'll try again later.

According to the post, the feature can be toggled on or off. Wonder if it's based on the Y!Q technology?
http://www.ysearchblog.com/archives/000074.html
http://yq.search.yahoo.com/splash/start.html