netmeg - 2:39 pm on Apr 30, 2012 (gmt 0)
Well you're never gonna get anything out of Google. They barely even explain themselves on the AdWords side when they give money *back* (and as an advertiser, I always get money back for the clients every month)
If you see large takeaways every day or at the end of every month, then there are definitely things you want to look at. If it were me, I would be looking at:
My ad placements; potential accidental clicks, ads that are a bit *too* blended, link units too close to menu or breadcrumbs, etc.
My traffic sources - is the traffic coming from the usual places, the usual referrers, with the usual keywords? My own sites are always tightly focused on geographical areas (usually US states) so if I see a sudden influx of traffic from China or Russia, I want to investigate that, because there would be very few valid reasons for it.
Possible botnets - I've been hit by this recently; the first thing I did was take the AdSense off the affected pages.
Other things can cause the take-backs as well; for example, if an advertiser doesn't pay Google, then you don't get paid either. It's unfortunate, but there it is.
It's aggravating to have them take money back, I know. The biggest reduction I saw was around a hundred bucks, but that was in an exceptionally high-click month, so I wasn't terribly surprised. Apart from that, it's usually less than a dollar. If I started seeing *regular* large take-backs, then I'd be worried my account could be closed.
Remember, you don't have to actively be doing bad things to lose your account. You just have to present a *risk* of invalid clicks to advertisers. That's a pretty broad statement.