According to http://en.support.wordpress.com/geotagging/ :
"Geotagged posts get marked up with the geo microformat, geo.position and ICBM meta tags, and GeoRSS and W3C geodata in feeds. All of this stuff is “machine readable”, not “human readable”; it’s hidden from view.
We’ll soon be launching a bunch of human readable stuff like theme integration, widgets, shortcodes, maps, etc.
Also, geotagged posts and profiles will be searchable in the soon-to-be-launched WordPress.com Geo Search."
That webpage is 4 month old, and I would like to know how soon is "soon"? ;-)
A rough estimation would be fine. I want to use a wordpress.com to track my summer trip and geotagging could be a really useful feature.
Thanks for the great job!