Memory
If we re-write memories every time we relive them, then photographs are the keepers and destroyers of personal memories. They perfectly preserve what that split second held- what everyone looked like, and the surrounding environment- but the conversations and internal reactions are subject to this re-writting process.
Videos preserve everything about the moment. So where does it stand in the memory spectrum? Pure, unaided memories are the most subject to change, photographs aid but also accelerate change by bringing up the memories more often, and video... I'm not sure.
You can listen to the podcast that inspired this at: http://www.radiolab.org/2007/jun/07/
(by the way, hello. sorry we haven't spoken since last year.)