It's not so much a matter of disagreement as being able to come up with solid counterexamples that a theoretical 'common person' would agree with.

For instance: If you want to get someone a gift for a birthday, it is a common social convention that the exact gift should be kept a secret from the receiver until their birthday.

As ChristianKI indicated, sometimes you must keep secrets either for social or professional obligations. A good example would be where doctors are required to keep patient records from unauthorized access (by law, no less).

Normally, people dismiss these sorts of arguments with a simple, 'Well, of course except for that.' As we move into the future, however, where technology increases to the point where surveillence is pervasive, is the only privacy we're going to have remaining going to occur in doctor's offices?