I realize this is an old thread, and sorry for responding to it years after the fact - but the same problem appears to be still occurring. I recently went to download Paint.NET after I reinstalled my OS and found that there is huge download button that leads to this site:
http://searchale.com/
...it seems to also use the referring URL to tailor the content. I got this when I clicked on the ad from the download page:
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Easily find
Paint Net Download
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Now, I know you can't necessarily control what ads get served up on your site, and I know that ad revenue and donations are what keep the site alive. Regardless, as a 'computer expert', I can't bring myself to recommend this software anymore if the people I am recommending it to end up feeling like they're being deceived - and deceptive is the only way ads like this can be described. I've made a complaint to Google, and I'm voicing my concerns here - whether that makes a difference or not, I don't know. As it stands, I'm already wary of recommending Paint.NET.