One example of that disconnect is that more than half -- about 55 percent -- of those surveyed falsely assumed that a company's privacy polices prohibited it from sharing their addresses and purchases with affiliated companies.

Assume the companies will do whatever will earn the most profits. They have expensive Lawyers to guard their privacy. The best defense can be knowing that advertising promotes what they want you to buy not what you want. When deciding to buy, compare, clean tracking cookies.
I also try and keep sales sites restricted to an Email address reserved for the purpose. It's silly to pretend this can be stopped, we are best off learning where information is used, and what information is given to those who don't need it.

Thank goodness for AdBlock Plus. I know the advertisers really object to it, but it is great!