The Business of Software ...
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you can block competitor ads from displaying in Adsense.
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If you are a mISV selling a product/service, is it really worth displaying AdSense on your site? You are essentially selling your visitors to someone else for pennies. The main way of making money from AdSense is when your visitors click relevant ads, which are most likely the ads belonging to your competitor.
(Terrell)
If you are selling a product (as opposed to content) you shouldn't be running ads.
(my name is here)