And don't forget the DARPA and Intel links to FB. The DARPA stuff was headed by Adm John Poindexter, at the same time that Gen Hayden was heading various Intel agencies. Hayden kept Poindexter arms length, as the latter was a controversial figure in the early 2000's.
National Journal reporter Shane Harris was doing (good, actual) coverage at the time and even wrote a decent book about Poindexter and his work.
Worth more digging on the intersections between DARPA, three letters, and possibly/probably FB.