Does displaying Google AdSense ads on your web pages cheapen your site? Not in my opinion. Some of the most reputable sites prominently display Google adverts on their pages. For example, see example pages on NYTimes.com  (the “Advertiser Links” section near the bottom of the page is AdSense) and Oreilly.com . The only danger with AdSense ads on your pages is that you are driving traffic out of your site. So, if you are trying to sell a high ticket item you might want to leave the ads out until you have an order — or at least an email address.
For those who don’t have etail transaction concerns, then Adsense makes a lot of sense (pun intended) for any kind of site that wants to monetize their rich content without having to charge a subscription for access. It is entirely possible to support a content site on AdSense revenue alone, a welcome change after years of popups and intrusive banner ads. For example, we own several content sites (e.g. WritersNet  and InnSite ) that collectively earn 5-figures from Google (actually from its AdWords advertisers, but the check comes from Google) each month. It’s “money for jam,” as Kiwis would say!