Bruce Schneier takes on the theory that loss of privacy is OK as long as it is mutual:
If I disclose information to you, your power with respect to me increases. One way to address this power imbalance is for you to similarly disclose information to me. We both have less privacy, but the balance of power is maintained. But this mechanism fails utterly if you and I have different power levels to begin with.
An example will make this clearer. You’re stopped by a police officer, who demands to see identification. Divulging your identity will give the officer enormous power over you: He or she can search police databases using the information on your ID; he or she can create a police record attached to your name; he or she can put you on this or that secret terrorist watch list. Asking to see the officer’s ID in return gives you no comparable power over him or her. The power imbalance is too great, and mutual disclosure does not make it OK.