This. Companies like to see big fat black numbers at the bottom of the balance sheet. They really don't sit around stroking a pet of some kind and cackling maniacally at their next scheme to put one over on those nasty consumers. Truth is, they don't care about you, they just want your money. If they see ways to get at it better, they'll use them. In this case, targeted advertising should be more effective,, since it will offer you stuff you want (if the targeting system is halfway smart, at least), so you would more likely be interested. Meanwhile, the company can save money because now they just have to advertise to the people who might buy their stuff instead of to everybody, hoping to hit the few % of consumers who need their product. Basically, it's smart missiles vs carpet bombing, and I think we can all agree that smart missiles should cause less collateral damage.
Oh, and before anyone gets the wrong idea: I am 100% against companies gathering (and holding indefinitely) personal data of people who did not give it up freely, knowing what they are getting themselves into. But I am also cynical enough to believe that a large percentage of Facebook, smartphone app, etc users would just shrug if you told them, and say they don't really care. Frankly, I myself don't much care if the corporate world knows I want to buy an inflatable pool, a bulk amount of whipped cream, and a used industrial vacuum cleaner. Let them make of that what they will. I do, however, draw the line at personal information I did not give to them. I do not want to receive mail/phone calls/creepy ads that state my (alleged) location/names of my close friends/etc, unless I gave that information to you personally.