For those of you willing to explore the issues of digital geospatial and cartograpic data preservation a new book has just been released online.  A big challenge to open data is data preservation.  Chapter 2, The Preservation and Archiving of Geospatial Digital Data: Challenges and Opportunities for Cartographers, was co-authored, by Tracey P. Lauriault, Peter L. Pulsifer and D.R. Fraser Taylor covers alot of ground, including a review of geodata portals.  You can read the book online for free!