Security through obscurity works because it takes time to defeat obscurity. The effectiveness of encryption, for example, is measured in the amount of time it takes to break it, not that encryption is unbreakable. We know with certainty that the processing power of a computer in just a handful of years will be able to break in a few minutes what would take hundreds of years today.
It is understandable, then, that the social contract concept is more difficult to understand when it comes to computers. I think this is in part due to the fact that to get into another person’s computer, I never leave my own keyboard. It is further complicated by the nature of digital information.