Finally got round to doing a slidedeck which I hope graphically demonstrates why traditional ad models are bound to fail in social networks.
It also illustrates the ways messages ought to be released into the wild if you expect them to survive (succeed) in a group-forming environment.
Of course, we don't just form groups in the digital world, but the internet is a more rapidly enabling environment on a global scale than most physical ones. But the two are coming together.
Further inspirational reading:
Here Comes Everybody (now only £8 gah!),
Everything is Miscellaneous.
Who said Americans couldn't do irony?