When it comes to privacy, it appears that legal change is coming.

Legal change typically follows rather than precedes changes in consumer and public norms. And increasingly we're seeing concrete indications that consumers are not just focusing more on their privacy, but also thinking about the concept in distinctly new ways. 

A recent survey by the Pew Research Center found that more than half of American adults who use mobile apps decided not to install an app because it demanded more personal information than they wanted to share. At Microsoft, we've undertaken similar research. It has shown that more than 80 percent of Americans believe that the tracking of personal information is out of hand, and consumers need easier ways to block it.

This has obvious implications for the development of new computing products, but also for the evolution of the law itself, with likely reverberations across many industries and businesses.

The constitutional protection of privacy under the Fourth Amendment is grounded in whether individuals have “a reasonable expectation of privacy” for certain information. To the extent that expectations change over time, constitutional protections typically evolve as well.

In the Supreme Court's January decision U.S. v. Jones, the court decided unanimously that the government's attachment of a GPS-tracking device to a vehicle constituted a search under the Fourth Amendment, and therefore requires the issuance of a warrant.

While five justices based this determination on more traditional legal principles involving a physical trespass, the concurring opinion by Justice Sonia Sotomayor captured where privacy is likely going in the future. As she noted, traditionally the Fourth Amendment has considered secrecy to be a prerequisite for privacy. Indeed, typically when people talk about keeping information “private,” they are talking about keeping it “secret.”

But people today are more comfortable sharing information than in the past. This does not mean, however, that they no longer care about protecting their information. The fact that individuals share information with some people for some purposes does not mean that they are comfortable sharing it with all people or for all purposes.

One often hears that a new and younger generation of people is more comfortable sharing information and has changed societal norms about privacy. While there's something to this, this notion is less than novel. When I was growing up in the 1970s, it wasn't unheard of for a teenager to share a piece of information with a friend but not a parent. I suspect this phenomenon was witnessed in the 1770s as well.

The biggest initial spark for change is not a new generation of people, but a new generation of technology. Computing products and online services have made it possible for people to share information with others, but with a new level of control. For example, one can share a photo online with friends while keeping it hidden from others.

Consumer expectations of privacy today are more focused on determining with whom one shares information and how the recipients can use the information that is shared. The fact that information is less “secret” does not mean that individuals consider it to be less “private,” it just means that people's thinking about privacy has changed.

As Justice Sotomayor concluded, when it comes to the Fourth Amendment, “it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties.”

As she also noted, because of the specific facts involved, U.S. v. Jones did not require a resolution of this question. But looking forward, the Fourth Amendment will likely evolve and influence the future of privacy rules and practices with implications for inside counsel across the economy.

Brad Smith is general counsel and executive vice president of Microsoft Corp.