It's a ethical question more than a legal question. Perhaps they did not buy the laptop, maybe someone else in their family did and they are merely a bystander.

* Do they have an expectation of privacy? * Does this violate this expectation? * As a deterrent for buying stolen property does this possible violation outweigh the benefit?

Consider a school which loans out laptops to its students but then uses the laptops to spy on the students. Or a company that backdoors its product so that when it is pirated they can spy on the users that pirated the software, perhaps uploading all their email to tumblr.

* Would such an action ever to ok? * Where do you draw the line? * What if you inform people that you are going to do this? How loud of a notification do you need to be justified (tiny sticker on the back of the laptop)?