Nothing really new for most of you, but still some good food for thought:
Cell tower records can pinpoint a phone owner's location for police, whether the phone is used or not.
Cell phone trails snare criminals, call or no — a nice article which tells us that several murderers were convicted using (among other things, I guess) cell tower records. Police could often pinpoint the location of the accused within a few blocks and thus "prove" they were lying in court about their location at a given time (i.e., their alibi was smashed).
Of course, this is not a reliable method in all cases. A murderer could give someone else his cell phone to create an alibi in the first place. I can easily imagine lots of other ways to abuse this.
While probably useful in some cases, this is pretty scary stuff. Authorities can track where you are at a given time, and where you are going in realtime. Combine this with Google Earth and you've got some pretty Big Brother style surveillance. This is inacceptable in general, but even more so if performed without probable cause (as has happened already). The EFF has some more information.
Issues like this always make me wonder whether I'm too paranoid or not paranoid enough...
(via Bruce Schneier)