I've heard somewhere that the amount of money you get per click on your adsense ads depends in part on link popularity meaning that if your site doesn't have a lot of links to it then the ads will make less money then usual. I also heard that the bot that is used to make this calculation does not change the cpc rating very often once it has made a decision as to how much of a % you'll earn per click on a given page. I can't find anymore information on this nor can I remember exactly where I heard this from (I believe it was an ebook). Can someone point me to a link where this is discussed in more detail?