[peteretep]

I suspect that an organization with the computational resources and mathematical clout of the NSA are going to have little trouble distinguishing between people clicking around on "J0llY R0g3rs Gu1d3 to NUKELERA WEPONS" and people creating specific, repeated trails to suspicious resources.

[jlgreco]

The idea, if nothing else, is that such an analysis is possible it is also expensive enough to make it hard to do for everyone at once. If everyone superficially appears to be searching for verboten stuff, then their job becomes harder than just "carefully investigate whoever is hitting naughty keywords".