It's just occurred to me that they probably have sniffer engines connected to Google that look for combinations of keywords, and when they find a match, the searcher ends up on a watch list or something.
In the course of researching my two books, I have looked up some dubious things. Off the top of my head, I can recall that I have Google mapped Faslane Naval Base (where the UK's nuclear subs are docked), tried to establish where the nuclear missiles are re-conditioned, enquired about killer satellites, and researched satellite earth stations and the surrounding areas. I'm sure there's more that I've forgotten about that should be added to the list.
Maybe I should start doing my research on public wi-fi from now on.
Interestingly, there are two men in trench coats and dark glasses coming this way. I wonder what they want...