Following up to my previous post about Google click quality investigation:

Google made another apparently superficial look at their data. They still insist that they "did not find evidence of automated activity or unethical behavior. Our data indicates that the clicks arrived from a variety of users and IP addresses."

I have repeatedly sent them the following arguments, which they have consistently avoided responding to directly:
I still don't understand how you do not find the correlation between blank referrers and poor performance suspicious. This is the strongest correlation evident from our logs, and it holds not only on the Saturday and Sunday in February when this activity was highest, but it holds throughout a 3-month range of dates, and it holds regardless of where the blank referrer clicks predominantly originate from. That Sunday for which you analyzed the logs, the blank referrer clicks were coming from Brazil, but on 2006-12-10, for instance, they're coming from China, US and Turkey, and the correlation is the same.

Likewise, the proportion of blank referrers falls to zero once we stop advertising on the content network, and it's not like we don't get any search ad clicks from China, Turkey or Brazil. But we don't get search ad clicks with no referrers.

You conclude from the fact that the clicks arrived from a variety of users and IP addresses that these clicks must be kosher, but this ignores that this is exactly the type of an attack that a savvy fraudster will mount. Who is to say that those clicks aren't coming from malware bundled with certain Brazillian programs? Who is to say that such malware was not designed to elicit exactly the pattern of clicks that is seen? You seem to ignore that fraudsters have had several years to adapt to all of your detection mechanisms, and that by now the skillful ones would be engaging in attacks of sophistication quite similar to what we see here.

If you CANNOT account for the strong, ongoing correlation between blank referrer clicks and the poor effects we see, then you CANNOT claim that these clicks are legitimate.
I can interpret their refusal to provide a reasonable explanation for this correlation in two ways - either they don't understand, in which case they are incompetent, or they know they have a major problem with AdWords and their strategy is to avoiding admitting it at all times and at all cost, in which case they are themselves participants in this fraud.

After all my insistence, they now credited our account with a one-time $500 "courtesy credit", which seems to be on the order of 10% of the amount we've lost due to this click activity.

So, yes, it does look like Google 'click investigation' is a charade which they operate largely as part of their public relations strategy rather than as an attempt to actually do the right thing and figure out what's going wrong.

No wonder they only ever 'find' 0.02% of clicks as being charged incorrectly. Once they've charged for a click, it is in their very strongest interest to insist that the charge was correct.

Ever heard how disk manufacturers advertise their disks as having a mean time between failure in excess of 1 million hours, which translates to less than 1% chance of failure per year? And then an independent in-field investigation finds out that the real failure rates are more like 2-4% and higher?

Meanwhile, Google founders Larry Page and Sergey Brin buy a 767 party plane and then argue about what kind of bed Brin can have in it.