Matt Savinar says his site is regularly visited by the CIA, DIA, and other government agencies.  Maybe just employees surfing in their spare time, maybe not.

I don't think it's automatic spidering, because I run several personal sites for friends and family, and I never see government agencies on the visitor source list.  Google, yes, the CIA, no.

A number of people I know with blogs have had similar experiences. Maybe they primarily spider sites that contain "speech" in order to look for potential dangers as defined by them.