Designing the internal social-networking site over the past few years at Lockheed Martin brought into focus the age-old security question of balancing "the need to know" and "the need to share," Dahlen and Mayo said.

-- which builds aircraft and missiles, among other things -- is a company with more than 150,000 employees. It has concerns about keeping information classified, so a small army of legal and security experts weighed in on the question of how to let employees use Unity to find out what was going on with their colleagues while at the same time safeguard the most sensitive information.

For starters, anyone using Unity will have ground rules, and one of them is "no anonymity," Mayo said. "There's no such notion as anonymous access."

So far, 54,000 U.S.-based Lockheed Martin employees have begun using Unity. Built on top of SharePoint 3.0 with Active Directory 2003, along with a search appliance, the Unity application allows people to post personal information about themselves, such as hobbies, interests and bios with photos, and link in with others who have common interests.

For business purposes, some material posted is reviewed by "Wiki gardeners" and blogs could be moderated. Some documents, such as those that might raise export-control questions, are locked so that only authorized personnel can get to them.