Back at school, there were all sorts of variously ethical electronic stalking techniques available, from the basically aboveboard to the downright sketchy. Someone once described the range of available options, along with the corresponding trails of evidence they left behind, as a form of submarine warfare: listening for ridiculously faint noises while trying to minimize the amount of noise your own listening created. Which would have struck me as a bit overboard -- after all, who besides submarine-skipper stalkers spends their days looking for other submarine-skipper stalkers -- except that I saw some fairly impressive demonstrations of CIA-level datagathering, most notably Ken's terminal-room monitor, which displayed a map of the terminal room, updated in real time, showing who was logged in at each computer, with the names of his friends highlighted.
That said, while there were plenty of resourceful lone wolves out there, tracking their quarry from kiosk to kiosk across campus, I'm not sure any of them quite held a candle to this one slightly whacked-out guy who decided to stalk the entire student population. By wiring together rwho, grep, sort, and a little Perl (ah, Unix, where everything is tools and pipes, and everything looks like it was built by a plumber reather than a programmer), he rigged up this script that would tell him everyone who was logged in from someone else's computer, and then dump the (name, friend's name) pairs into an ever-growing list. It was kind of a pointless exercise: the list got incomprehensibly large, thousands and thousands of pairs, good basically for telling you that yes, you and your roommates all logged in from each other's PCs now and then. He had some sort of vague plan about eventually doing some statistical analyses and computing the degrees-of-separation index for the student population; I'm not sure whatever became of that. Whenever I think about computers and privacy, this story is one of my starting points. I'm not sure quite what to make of it, but it seems to me that while the individual bread crumbs we leave behind on our electronic wanderings may be insignificantly small, there are scavengers out there figuring out ways to reassemble whole loaves.