[UPDATE: After several months of this Google finally raised the cost-per-click on my underperforming ads above my $1.00 daily budget, so I ended the campaign. The final stats: over tens of thousands of impressions, my net CPM (cost per thousand impressions) for these highly targeted ads was $0.36. That's not free, but it's really, really cheap. My conclusion: there's something to this strategy, and I may well use it again.]
I wanted to understand clickfraud a bit better, so I started advertising this blog on Google and trying to see what sort of fraud it could catch. Then when I had finished the experiments I left the ads running. Now I've just checked the latest stats, and I appear to have found a loophole in Google's revenue model. I seem to be advertising on Google for free.
Google ads are pay-per-click. They're based on an auction model, so for each keyword/phrase the best performing ads (some combination of those that generate the most clicks and those who will pay the most for those clicks) rise to the top, displacing others. For popular keywords, I'm sure that's an efficient, highly-optimized model.
But I chose a bunch of very obscure terms to advertise against. And my ad sucks (see above) and nobody ever clicks on it. The result is that I get hundreds (sometimes thousands) of highly-targeted impressions a day for free. Every now and then Google notices that my ad isn't performing, so I have to raise the price I'll pay for each click (I'm now at $0.40). But since I get no clicks it doesn't matter.
I have to admit to a slight rush of pride that I've managed to outsmart Google in some tiny way and get free impressions. Granted, the value of those impressions is at most a couple bucks a day. And because my ad, as mentioned, sucks, the actual benefit to me is probably close to zero. Furthermore, if anyone were to actually click on the ads, I'd quickly lose whatever gains I've made (if you do happen to see my ad out in the wild, please don't click on it). But still! I've hacked Google! Woot!