The FTC Tech-ade hearings  have brought out a wealth of questions surrounding privacy issues, and today I would like to highlight two of them. We have never had a universally accepted definition of "personally identifiable information," and the rapid evolution of technology only seems to be plunging this debate into further confusion. Michael Geist of the University of Ottawa (among others) noted yesterday that even systems that appear to protect users from being identified -- usually by correlating users to pseudonymous unique identifiers instead of to their own names or data -- are vulnerable to data mining techniques that can reveal users' identities. Today's panel on computing power brought this discussion to a whole new level. As part of a discussion about sensor networks, Deirdre Mulligan of U.C. Berkeley mentioned a project she was involved in that used sensor networks within the home with the ultimate goal of finding ways to reduce power usage. By reading data gathered by sensors about things like heat and light, she was able to infer when a house's inhabitants came home from work, when they got up in the night to tend to their small child, and other similar information. We certainly don't currently consider this kind of data as personally identifiable, but consumers may justly feel that their privacy is at risk if this type of data can be made publicly available (or even available to the power company). In the coming decade our policies and self-regulatory structures concerning data privacy will have to take these kinds of issues into account. The second question that has come up repeatedly thus far concerns whether consumers' notions of privacy and are changing as technologies change. If millions of consumers are willing to divulge intimate details about their lives on blogs and social networks, does that mean they no longer value their privacy? The answer depends on whom you ask. Wall Street Journal technology columnist Kara Swisher gave her take on privacy as she moderated a panel yesterday: "There is none." Several other speakers agreed that evolving technology can drastically diminish our standards and expectations for privacy, and as more and more personal information is made available over the next decade, these will continue to change even further. On the other side of the debate, Marcia Hoffman of EFF and several other speakers expressed their belief that the increased availability of personal information does not necessarily mean that consumers don't value their privacy. Revealing information on one site or in one context does not necessarily indicate a willingness to reveal information everywhere, or a generally lax attitude about data security. As the technologies that we learned about at today's hearings - sensor networks, artificial intelligence, RFID, highly targeted marketing - continue to evolve, so too will consumers' conceptions about what privacy means them in all kinds of contexts.