Re:Nothing to see here, move along... (Score 1)

I fail to see the logic in that. Oh look, he bought , that means he must like , let's bombard him with offers for MORE of . If I just bought one, it's actually LESS likely I am going to buy that same kind of product again...no matter how many ads.

Knowing your purchasing history helps see what kind of products/services you may be interested in either now or at some point in the future. This is more about direct marketing on a one to one basis than it is about advertising in a more traditional sense. If anything, profiling for advertising helps deliver ads for products/services you are more likely to be interested in than ones you aren't. It can also help better target buyers of consumables that are currently purchasing from competitors. Look at grocery stores that spit out a coupon for laundry detergent X at the cash register after you've just bought laundry detergent Y. Online - just a few examples - music downloads, software, books, dating services, employment sites, wedding services.