Well I have several sites, some of them I apply the AdSense to; to make a few extra pennies and some of my websites I wouldn’t even dream of placing Adsense to.
For example, I will not use AdSense on a site that I wish to sell one product on, especially my own products. This can take your potential prospects away from what you want them to buy. Why would you risk losing them to your competition or to another site for a few lousy cents? Or dollars if you got the “higher” end priced AdSense ads on your site.
All sites where I am selling a specific product will not have any out going links for me. I want to keep them on my site for as long as possible.
However, I will use AdSense on sites that are more along the lines of “Free Content” websites. Usually these websites I set up, I use directly for making money with AdSense.
What’s interesting with AdSense is that your layout can have a detrimental affect on how much you can earn from using it. Of course testing and re-testing will be your ultimate tool in finding out what works best with your website.
I tend to stay clear of the lay out that looks like Google’s sponsored ads on the main Google website. Everyone identifies these ads as “paid” and not as likely to have as many people to click through them.
Adsense can be a nice little profitable tool if used correctly.