No smart company, like Target, is selling your personal info. That's not what this article is talking about. This article is talking about analyzing they way you use a company's website and/or retail store, recognizing trends, and promoting products to you based on what they think you're shopping for. If they're giving info about you to any other companies, it's almost always so that that other company can drive a marketing campaign on behalf of the advertiser that targets you as a customer.
Probably the most well-known example of this is a company called Criteo. If you go to Zappos.com and shop around some of their shoes and then leave the site, you'll notice that Zappos is suddenly following you around the internet. That's what Criteo does - they gather data from Zappos and buy ad placements. When you view one of those ad placements, Criteo is like, "Hey, I know this guy, he was on Zappos looking at some sweet New Balance trail runners. I'm going to show him a bunch of trail running shoes."
In this scenario, Zappos wins because their ad money is being spent on an ad that you might actually be interested in. And you, the consumer, wins because you're seeing offers that are actually interesting to you, instead of seeing some ad for some super heavy all leather hiking boots.
Very few companies are selling your personal information these days. Except for magazines - selling customer info is a big part of the magazine business. But outside of magazines, there's just not much of a market for personal info for a couple of reasons. First, your address doesn't tell me nearly as much about you as how you use my site does. If I do my job as a marketer right, it's not all that hard to get your address info, and thus not worth paying for. Second, other info, such as how you use some other site, is always suspect data because we know that you won't necessarily use our site in the same way - there's just too many variables.