Watching the most "dangerous" people is also a very useful technique.
They do that by infiltrating the independent groups and even providing some resources for them, keep them close so they can watch them and detect any breakthroughs. Examples of dangerous people in the BF world would be the highly motivated go-getters, persistent, independent thinkers who are willing to go out and look for themselves. They would be targets to keep an eye on.
MIB, Hiflier, Norseman, Explorer, WSA, SWWASAS and BigTreeWalker are dangerous. How would you keep an eye on them?
Befriend them, give them a place to gather and share their thoughts and discoveries. Then you can easily monitor what they are doing/thinking. Get their data and store it conveniently.
I probably shouldn't bring this up, but if you look at the BFF leadership and some of it's most dedicated members, it's somewhat concerning...
Director: MasterBarber --> LEO (never comments, but is always watching)
Steering Committee Chair: Hairyman --> USFS official (never comments, but is always watching)
Administrator: VAFooter --> LEO (never comments, but is always watching)
SSR Data Curator: BobbyO --> Private Security (he's from England / Asia with a commitment to BF?)
SSR Analyst: Redbone --> a mysterious person, nobody knows exactly what he does.
Best Donor: JDL --> Military
huummm...