"We have been contacted by the military," Google spokesman Larry Yu said. "In those instances where they (the U.S military) have expressed concerns about the imagery, we have accommodated their requests."...
The images that worry the Pentagon include views of bases, including security at the entrances to those installations.

"It actually shows where all the guards are. It shows how the barriers go up and down. It shows how to get in and out of buildings," said Renuart, commander of U.S. Northern Command.

Air Force Gen. Gene Renuart, chief of the U.S. Northern Command, said Thursday that that the decision to issue a formal ban was made after at least one Google crew requested and then was permitted access to a base, identified in the message as Fort Sam Houston. He said he was concerned that allowing the 360-degree, street-level view could provide sensitive information to potential adversaries and endanger base personnel.