Here is a New York Times article on Google and its dominance of the Internet.  The reality is that everyone who wants to get business from their website has to pay attention to Google.  Because Google changes their algorithm frequently a "build it and let the website sit there" approach no longer works.

This is because of the changes Google makes and the need to adjust, but also because there is so much money being made through websites that if you are not keeping up and your competition is, your site will fall in the rankings.

NY Times Google Article