weeks - 1:37 pm on Jun 7, 2011 (gmt 0)

This could help Google grow their display advertising business much like acquiring Urchin helped grow their paid search advertising business.

This sounds right to me. It's likely that PostRank sold themselves to Google as much as than Google bought PostRank. Using the Google $ and brand as a base is a good way for the players at PostRank to move to the world stage with their ideas and talent. Thus the move to warm and sunny Mountain View.