Do you know how your cellphone works? If not, it's probably best not to find out. You can lose your constitutional rights that way.
That, says Jacob Sullum, is the implication of a recent federal appeals court decision that said the government needs a warrant to obtain cellphone location records. While the conclusion is welcome, Sullum writes, it can be reconciled with Supreme Court precedents concerning voluntarily disclosed information only by assuming that people do not understand that their cellphones are also tracking devices.