I once put AdSense on my RSS feed - it linked to about 200 files. EVERY file linked to had a 336 ad right after it. So, 200 ad block impressions for a SINGLE RSS file view. Times four ads per 336 impression, equals 800 ads total.
I immediately removed AdSense from my RSS file, my mouth hanging open throughout the removal. I'll never try that again.
Not trying to "one-up" anyone here, but I was blown away by this. Several years back now. I specified one ad block, and somehow it became one ad block PER LINK.