AdSense Optimization Report and MFAs
If you’ve logged into your AdSense account recently, you may have noticed a new section called “Recent Messages” on your “Reports -> Overview” screen. It should look like this:

This is what my optimization report says this month:
April 2007 Optimization Report
Dear Publisher,
Here is your optimization report for the month of April. After an automatic review of your sites, we think you might be able to improve your monetization using the following tips:
You may be filtering ads that monetize well on your site.
How can I fix this? Dismiss this tip.We hope these tips are helpful, and encourage you to experiment using different layouts and formats–no two sites monetize the same way!
Sincerely,
Google Adsense
This is in relation to the URLs I have in my Competitive Ad Filter.
A quick recap
The competitive ad filter allows you to enter URLs for sites that you don’t want advertising on your site. For example, let’s say you run a site that talks about golf, and you notice that you’re starting to get a lot of ads from a “VW Golf” car advertiser (unlikely, but possible). This isn’t really relevant to your site, so you’d like to block this advertiser from your site. To do this, you’d log into your AdSense account, click on “AdSense Setup” and then “Competitive Ad Filter”. At the bottom under “AdSense for Content“, you would enter the URL for the advertiser that you want to block in the “AdSense for Content filters” box. For example, if you notice that the “VW Golf” advertiser’s URL is www.vw.com, you could enter “vw.com” into the box, and it will block all ads that point to this site…
Decreasing Profit
But, remember that it’s not only you that makes money when a visitor clicks on an ad. Google is taking a nice slice of that pie as well. So, it’s in their best interest to show the ads that will generate the highest income. So, blocking a specific advertiser might mean that Google will have to display a lower-paying AdSense ad on your site.
Blocking MFA sites
Ok, fair enough. I might be blocking ads that will have a higher CPC than the ads I currently have showing. The problem is, on the sites where I’m showing AdSense, I’m not really blocking competitors, but rather blocking sites that I don’t want visitors going to, such as MFA sites.
MFA stands for “Made For AdSense“, and these are sites that generally don’t supply any information, but show a LOT of AdSense ads, in the hope that the visitor will click an ad to find more info… And, most of the MFA sites that I’m blocking are using a technique called “AdSense Arbitrage” which is where they will pay perhaps 3c a click to get the visitor to their site, and receive (hopefully) 10c or higher when a visitor clicks an ad on their site. You can find a bit more info on this subject here: “AdSense Arbitrage: Tips, Tricks & Secrets”
The Dilemma
Now, because Google is suggesting that I might be able to increase my profit by unblocking some of these sites without telling me which ones, I have to decide whether to send my visitors to MFA sites. I would decide not to unblock them, except that, according to this thread on WebMasterWorld, people think they are seeing that Google is punishing them for having a lot of “blocked” sites.
It could just be that the genuine advertisers are using all their skills to optimize their ads, and thereby be allowed to bid a LOT lower for their ads. With Google’s “Landing Page Quality Algorithm“, or “Quality Score“, advertisers with quality content on their landing page (and site) will be able to pay a lower cost per click. So publishers (like me) will have to suffer a little to ensure that their visitors who click on the ads will be taken to quality sites.
Is this a price you’re willing to pay?

Very interesting. I too have definitely been punished for having a large list of blocked advertisers. The thing is, every one of them was a spammy, MFA or very low click value site. As an experiment I unblocked them all and – POW! – traffic went up by 25% the next day. A coincidence? I don’t think so.
The only problem was that my earnings plummeted. After a few days I was getting a pathetic 2c per click average. Why would anyone bother writing good quality content to be paid that? So as far as I see it, Google needs to pull their finger out and sort the crap out. If Google can’t do it then let us do it.
Thanks for the comment, Steve. And I agree with you. After deleting my “blocked” list, my CPC fell, same as yours. So now I just ignore the “optimization report” every month, because I’m NOT deleting the MFA’s.
Even if Google is supposedly going after them. Because MFA might stand for “Made for AdSense”, but I reckon they’ve just switched over to other advertising networks.