seth godin is spot on, yet again. this is a great example on how blogs and PR agencies (or their clients) work together. it starts out with favors, but it usually ends in business clinch.
The most corrosive sort of this network amplification goes like this: I do something for you unasked. Then I do something again. Perhaps I even tout you or your work a third time. Then I come to you, point out how generous Ive been and ask for you to do something for me. Or I network my way to one person and then use that platform to reach three more, and repeat until Ive worked the entire digital room.