The act of using the Unix finger command to keep track of someone's movements, occasionally because of romantic interest or a good old game of assassin. Can be aided by a good stalk script. This activity is most commonly engaged in by students at university who would like to find out a little something about a potential crush, the movements of a wandering SO, or who just like to freak out their friends by describing their movements to them*.
This phenomenon was highly popular at Harvard College prior to the advent of roaming ethernet, which made it much more difficult to figure out where someone was. While one might expect that this activity would be confined to the geek segment of the population, nothing could be farther from the truth. Pine has long been the mail reader of choice at Harvard, and so most students are accustomed to logging into a prompt (even if they weren't quite aware that this was what was going on; common instructions given by a UA to a clueless user in order to get a prompt was to 'get into pine, and then quit without logging out'). So, through the grapevine or through the intervention of a friendly CS major, most people eventually learned about the functionality of the finger command. The most devoted finger stalkers I knew during my years at school were not love-lorn male geeks, but boy-crazy female liberal arts majors (sorry, 'concentrators').
In the days prior to the arrival of ethernet roaming, students ethernet connected machines had names based on the students username. For instance, my laptop was known as collier.student.harvard.edu. This fact, combined with the addiction to email common among college kids meant that it was quite simple to find out whose room someone was in, or if they were hanging around in the Science Center at a kiosk or the terminal room. If a roomate failed to come home one night, you simply fingered him or her, and the source of their late-night nookie was revealed to you- based on the fact that your missing roomie had logged in from the computer of that cute chick from Ec 10 before going to class at 9 A.M. Through judicious finger stalking, you could figure out someone's daily schedule, where they slept most of the time, who they hung out with, who their roomates were- information that may or may not have been available otherwise.
Reverse finger stalking became a common activity as well; by checking when the .plan file had last been accessed, one could discover who had fingered you last. By cross-referencing a list of suspected stalkers with the output of a last or a no-argument finger, you could take a crack at figuring out who was finger stalking you. This method was easily frustrated if you showed up on too many stalk scripts, however.
*: Certainly, we were never so crude as to pipe the output of yes into a well-placed write, thus clobbering your poor victi- er, friend's terminal display. | 
