For a top search engine position, you have to please the search engines. But to make web sales, you have to please your customers.
Search engines change very quickly.
They change formulas, formats, even partners. It could make you crazy to keep up with them. These principles apply to almost all SEs. They are so closely connected with the essence of what SEs do that they'll continue applying for the foreseeable future. And IF you follow them carefully, they'll keep you on the first page of search engine results when YOUR customers are out there looking for you.