Adsense stop words trigger Public Service Ads which gives you nothing when someone clicked on it.
I have this problem with one of my blog post before because it has stop words in it. Even if the traffic is high, I get nothing and loses something (bandwidth). The traffic is huge because I was able to optimize it for a highly competitive keyword: naruto porn. (I simply make a blog post condemning it. LOL!)
Now, the problem is solved. What did I do? I used alternate ads. When Google doesn’t want to show their ads, you can configure them to show an alternate ad. And on my case, I used Widgetbucks as an alternate ad. Now, horny people searching for naruto porn has something to click when they come to my blog post. Hehehe.
If you want to learn how to do this, Google Adsense help provide a detailed step by step procedure here. Just follow them and you’ll not get lost. Or if you get lost, ask me.