Str82u - 4:51 pm on Jul 2, 2012 (gmt 0)
I'd rather see discrepancies than an email from Google to say they have suspended/banned me for no fault of my own.
We had a month that was about 10% short, the two months prior was roughly 4-5%, enough that we just assumed it was going to be that way forever, some new algorithm in adsense. We also suspected we were at fault because of a "drydock" site were we develop for a live site and the ads were displaying (we block traffic, we are the only ones seeing ads)... we replaced the ads with blanks like we should have in the first place and everything settled down to less than a 1-2% difference after that.
Another thing about invalid clicks, related to what @Lame_Wolf posted, I've suspected competitors trying to cause the invalid clicks and subsequent cancellation of the AdSense account but I think that the AdSense team can see that too.
In regards to AmazonAWS, I've heard rumors that they duplicated some site's content as well as "clicking" ads as part of following links, both are totally unconfirmed on my part.