10gb presentation copied to a flash drive, 10 minutes. 10gb presentation burned to Blu-Ray, half hour. Then you must have a machine with a BR drive to run the presentation. I doubt that everyone is sporting a BR-ready machine just yet, especially in the .gov or .mil.
It's not hard to have a 10gb presentation when dealing with coporate level (or upper-echelon.gov level) settings. A bunch of large image files, couple of video clips, sound files, etc, and you can hit that number pretty quick.
Brad