Targeting is about maximizing profits for the advertisers, it's not about maximizing value to you. If they can use targeting to take value from you in order to give it to themselves, they will. For instance, you could be bombarded with targeted ads for product A when you'd really be happier with product B. You can contrive scenarios where ad targeting is a win-win, but those scenarios are misleading because they go against the underlying incentives.

I wouldn't mind a neutral, personalized product recommendation engine, but that's not what ad targeting is.