Full details are under NDA, but some information has leaked out about the new Google Maps Data API. The API has been described as "AtomPub" - an XML/KTTP protocol for readwding/writing feeds. The API allows for the storage of geospatial data, different geometry types, searchable with Google Maps, batch operations, unlimited attributes, and incremental updates.

The Directions Mag posting with further information can be found here:

http://apb.directionsmag.com/archives/5611-New-Google-Maps-Data-API.html