The US intelligence community actually keeps a clone of Stack Overflow that is updated every 12 hours and copied to servers on the classified version of the Internet so that people developing classified software can use it without needing to turn around to their unclassified workstations. I'm sure they're not alone in this, so the entirety of the answers there could be restored from mirrors or just used from the mirr…
On top of that security, it'd also be interesting to monitor what someone (based on their IP and browser fingerprint) was looking up on SO, you could probably figure out what they were working on that way.
Although I guess when you work for the spooks, they could figure out how to mask your IP that each query would come from a different IP from the world (basically I'm describing Tor, I wonder if they have their own Tor network).