Marshall Kirpatrick argues that even studies in anonymous aggregate must be opt-in.

Privacy is only going to become of increasing importance to be protected from digital intrusion. Not just from the state but from other organisations as well. I would not be surprised to see it become entrenched as a political right. It already is in some locations; the whole Swiss banking system is predicated on it.
More reading: Tags, Privacy, Cell Phones
Cam Riley: South Sea Republic. Freedom, liberty, equity and an Australian Republic.