So someone gets robbed, then they subpoena the web logs for pleaserobme.com, and then they arrest everyone who visited the site? That doesn't really scale.
Not for finding the robber in the first place, but it's going to look very bad if the police think it's you and then confirm that you visited the site just before the burglary.
lol no, it does not scale nor does it have to - person X commits a crime, they go looking for "evidence" and criminals try to avoid leaving this "evidence" and tend to be very paranoid about it, thus the joke..............................................................................
