toomer - 12:08 am on Jun 28, 2006 (gmt 0)

Tho' I am sure there are exceptions, the ads that appear are generally those that bid highest

Actually, based on my read of AdSense - this is actually not how things work. AdSense picks what it "thinks" will earn the most money. I would guess that is based on two factors - the CTR % of the ad that the advertiser is running in AdWords, and the $ CPC. Some ads might have a low CTR - but the bid price is high. Others might have a low bid price, but get a high enough CTR to compete as well.

AdSense picks. As a publisher, I get no say (and I'm both a publisher and advertiser as well).

The problem with this, I feel, is somewhat similar to my GPS nav system in my car. I tell it where I want to go -- and it determines what, in its opinion, is the "best" route for me to get there. Sometimes it's the fastest - based on calculated time. Other times, it's the shortest based on mileage. But it picks for me - based on what it thinks is best.

You know what? A lot of times, if I am very familiar with the landscape I'm on -- I know a way that it slightly better. And in some cases, much better.

So let's look at an example scenario. Let's pick a popular subject - iPods for instance, and say that I'm running a single 1-unit ad block on my page. So AdSense can only choose 1 advertiser's ad to display.

Let's say one advertiser "A" actually sells iPods, writes good copy, and has good prices. For sake of argument, let's say his bid is $1.00 per click when his ad lands on my site. Now let's take advertiser "B" that runs a MFA site about iPods, or a "free" or "rewards" offer site for iPods. His bid is 10.1 cents when his ad lands on my site.

Assume, for sake of argument, that advertiser A gets a 1% CTR on his ads, and advertiser B gets a 10% CTR on his ads. Guess what that means? All things being equal, advertiser B - the "junk" advertiser, as commonly referred to here - will end up paying me one penny more than the advertiser with an actual product.

Now, is that worth it? That extra penny? Some may think so. Some may not care that their visitors are about to plunge into a 400-spam-a-week deluge if they sign up for that "free" offers deal. But for me - I'd prefer to not have that penny.

Please take all of this with a very large salt-shaker, as it's all hypothetical... but this is just how I see it.

Now, add in another factor - just to complicate things more. Let's say that your web surfing community is (and I hate to make generalizations) more towards the right-end of the IQ curve than the center. They're probably going to more in-tune with the fact that you don't really get anything for free - and are probably less likely to click on advertiser B's ad on my site. So now, I am actually earning less at the end of the day - because that advertiser's ad does well elsewhere but not with my crowd.

There's countless examples that people have posted about their revenues going up after they've blocked MFA's and junk ads - even though AdSense thinks they'd be better for our sites. My traffic numbers aren't large enough to draw any sort of statisical conclusions from ... but I'm starting with the blocking from day one (and have noticed a decrease in low-paying clicks) and at some point in the future when I do have traffic worth mentioning I'll be glad to pull the plug on my block list for a few weeks and see what happens.