What is 'Open Source Marketing'?

I caught up with James Cherkoff last week, and we quickly got to discussing a meme I'd heard a couple of times before: 'open source marketing'. I asked what he meant by the term.  This is his best answer so far:

"When was the last time you saw an advert so good that you wanted to be in it? 

...[ipodmyphoto is] a perfect example of a group of customers taking the foundations (or source code) of a campaign (style, imagery, copy) and building on it in innovative ways that amplify the original message. At no cost to the brand. The question is how this can be achieved intentionally by brands that don't have the natural fanbase of Apple.

Watch this space for the answers."