I can see definite advantages and disadvantages to companies tracking my likes and dislikes via search engines, social media sites, etc.
On the one hand, keeping track of different criteria certainly helps with customizing advertising to my liking. By keeping active tabs on the kinds of things I search for or view, they can better adjust their marketing to suit me personally. I know when streaming video, I'd certainly prefer watching an ad for LittleBigPlanet 2 or Inception over something I don't care about in the slightest like cat food or baby wipes.
On the other hand, the idea of a corporation basically having full access to all my previous searches is incredibly unnerving. Not to mention that if companies like Google are keeping track of searches made, who's to say that these searches will be kept under lock and key, and not sold to other I still remember recently when Facebook app Farmville was found to be leaking personal details entered by its users to other 3rd-party companies. Even further back, AOL inadvertently leaked the history of searches its users made back in 2006, and some particularly embarrassing things were tied to certain individuals. I've looked up things related to some very personal issues before, and I can't say I'm entirely comfortable with sharing this kind of faceless corporations, let alone unrelated entities or the general public.
While I can certainly see the business advantages to keeping tabs on your customers' tendencies, I gotta say I'd be much more comfortable sitting through one or two ads for bran cereal than I would be giving away every detail of my life to advertising companies.