I have an issue with the notion that something should be allowed because it is possible. Yes, it is possible to collect the data about my buying habits. But should it be allowed? It is also possible for me to ram a knife into your chest, but should that be allowed?
For a long time, we didn't think about the consequences of wholesale collection of all available data of people, because the sheer amount of data meant, that it wasn't done for all people in the most complete manner. There were specialized professions which collected as much data as possible, but only for a certain subset of people: tabloid journalists for celebrities, spies for high profile persons in politics, investigators for people accused of a crime and private eyes for targets the paying customer named. And we thought, that those limits somehow made sense, as most of us are neither celebrities, high profile persons in politics, accused of crimes or in an enduring conflict that makes one side willing to pay large sums of money to private investigators. And we somehow felt, that those persons are special, and thus permitted special care, and we told ourselves, that those persons deserved it because of their life choices.
But with the availability of data storing and processing, we all are now in the role of celebrities, accused, politicians or people in deep conflicts. Suddenly it's not a choice anymore to get your privacy constantly violated. It happens to all of us. And now we see that the old idea, that if something is in the public view, it belongs to the public, and it should be allowed to indiscriminitely record, store and process it, is working against us.
About 300 years ago, we understood that for special types of data, it shouldn't be the case. Works of Art were in the public view, but it was explicitely forbidden in the Statute of Anne in 1710 to record, store and process them without explicit permission, because mostly everyone understood that those works somehow incorporate a value.Now with the advent of big data, we also see that other data, which are not Works of Art, still have an intrinsic value, and if everyone is allowed to siphon it from us, we lose, and someone else who is not us, gains, albeit it's us who created the value in the first place.