I assume you're talking about the passage at http://plato.stanford.edu/entries/privacy/#PriHumDig
According to Bloustein, Warren and
Brandeis failed to give a positive
description of privacy, however they
were correct that there was a single
value connecting the privacy
interests, a value they called
Not being a lawyer, ethicist, or philosopher, it seems to me that the term is an attempt to abstract that part of an individual which holds a right to privacy - not everything we say or do is subject to privacy (for example, a public statement made by you can then be reported freely by anyone to anyone), but there is an 'inviolate' aspect of the individual (for example, a private conversation cannot be recorded without agreement by both parties).
Obviously, the exact extent of the 'inviolate personality' versus the 'public personality' is something rather vague, and a lot of time is spent in courts and governments concerning the protection of these privacies.