DigitalGlobe filed this week to go public on the New York Stock Exchange under the ticker DGI, with an IPO of up to $250 million.  The company owns several high-tech satellites that generate massive amounts of high-resolution imagery of the earth’s surface.  From D&N’s perspective, the ‘geo-content generation’ business is a curious one.  No doubt it takes a great deal of money to build and deploy such sophisticated satellites, yet most people think maps should be available at no cost...