It's happening both ways. Political data is making its way into commercial ventures and marketing, and the consumer behaviour data gathered by Toys“R”Us or whoever is making its way into political campaigning purposes.
I don't believe there's much of a problem with going door to door and knocking on somebody's door and gathering that data. You can't scale that out exponentially, because you're limited by time and space.
I don't know what gun laws are like in Canada, but in America we have the concept that you have certain guns that are okay to own, but we don't allow civilians to own machine guns. It's the same type of thing. You can have knocking on doors and gathering the phone number of one person at a time or whatever, but when that turns into more of a machine gun situation, whereby you are sending out thousands of surveys and emails and Facebook advertisements and everything and harvesting en masse the private details—or personal details, at least—of many, many thousands of times the people you could normally reach, that gets into the machine gun category, and that is dangerous.