My new article When AdSense Makes No Sense describes common scenarios where it may not make sense to use AdSense. While it's certainly a great pay-per-click system, AdSense is certainly not the only solution out there and it may not be the solution that best fits your needs.
The article can be included in newsletters and posted on websites for free, see the license at the bottom of the article for more information, or send me mail for more details.