GT: If you receive an invitation e-mail from a social networking website that you've never visited, and found the service just reached you via tracking your friends' or acquaintances' MSN contact lists without their permission, do you think your privacy has been violated?

Acquisti: Privacy is about boundaries of public and private. Those boundaries are naturally fluid and change across individuals, cultures and times. So, the issue of whether what you describe constitutes an objective violation of one's privacy has no simple or determined answer.

I would rather try to separate the legal, ethical, and practical issues, and reply that such initiatives may be illegal under certain privacy regulatory regimes and totally acceptable under others; most likely, they will be annoying to the end user.

In the short term, privacy violation may seem like a quick and easy way for a new social network to gain new users, but in the long run they could end up proving to be a destructive strategy, if the social networking sites loses the trust of its users.

GT: You argue that almost nobody uses privacy enhancing technologies and people actually do little to protect their privacy even they claim to be very concerned about it. And you think this is because privacy is an economic problem. But the protests show that many people don't want it economized. How do you perceive these people's idea on this problem?

Acquisti: Internet users do engage in protective strategies, such as removing or obfuscating data, but, in general, PETs that help you protect your data have been obviously much less successful than applications, such as online social networks, that help you broadcast and spread your data.

The dichotomy between privacy attitudes and behavior has become known as the privacy paradox. Among researchers, many reasons have been suggested to explain this paradox.

In my view, there is not a single reason why people claim to want privacy and seem to act otherwise; it's a combination of factors, ranging from awareness and knowledge of data uses and abuses, to perceptions of control, to cognitive and behavioral biases in decision-making.

This is why I have an interest in the so-called behavioral economics of privacy.

GT: Do you think those advertisements and services that are tailored for personal preferences are good or bad? Can we find a way to balance Internet privacy protection and these specialized services? Do you think the solution to Internet privacy protection and application should be a technical one or a legal one?

Acquisti: I think that the targeted ads and services are neither good nor bad in theory. It's only in practice that you can measure whether they are either advantageous or not to consumers, that is, whether the benefits outweigh the potential costs, be they tangible or intangible.

And yes, there are ways to gain the benefits of targeted ads without having to reveal everything about yourself. It goes back to the issue of privacy enhancing technologies, but technology does not necessarily work without the proper economic incentives and an adequate regulatory framework.

GT: How will the dispute affect social networks' future development? China's social networks almost all adopt the pattern of US social networks, but in China website companies' violations of individual privacy haven't raised public attention. Will the dispute in the US change China's social networks' development?

Acquisti: This is a very interesting issue. How innovation in global information technologies is shaped by, or rather shapes, the cultures that adopt those technologies.

By using Facebook, will Chinese users eventually take an approach to privacy and information disclosure that is more similar to US users, or will Facebook adapt to the Chinese market and adopt some of its customs? I do not think we have an answer yet, but it is a very good issue to think about.