Jakob Nielsen probably knows more about the psychology of the Web (how people use it) than anybody else in the world. So when he says, "Search engines are leeches," it is a good idea to pay close attention.
Nielsen has actually done the math to show how search engines like Google make more and more money at the expense of the businesses placing ads. In a detailed analysis, he even shows how redesigning your site to improve the user experience and to make the site easier to sell your products or services tends to make Google more money than you.
If you advertise on the search engines, read this article carefully. At the end of it, Nielsen provides some strategies for weaning your company/organization off search engines.