Adsense operates as auction,the highest bidder gets to show ads on your website. Your website has a "fixed" supply of ads to fill, thus the more participants in the market, the higher the demand for those ad slots. As demand increases, for a fixed supply, so does price. Blocking ad networks from participating in the auction for you ad slots reduces demands while keeping your supply fixed. The result is lower prices.

You may believe that blocking an advertiser (or network) that pays very little is beneficial to you, but it is not, the ad or ad network, that you blocked is quickly replace with the next ad in the queue, which will pays less than the previous one.

This is not to say that there aren't valid reasons for blocking ads or ad networks, such as eliminating spammy ads. But blocking comes at a cost to you. It is certainly not a good idea if profit maximization is your goal.

Hi NickMNS,
Your number of VOTES top my number of POSTS. I really seek competence and accuracy here.

So, I am turning them all on, to follow your advice.
Can't hurt, right? Much.

How long should I wait before reporting my new results here. Should a week do the trick?
Off to flip some switches.

EDIT: (from Help)
To allow or block ad networks:
1. Sign in to your AdSense account.
2. Click Blocking controls.
3. Click your product. For example, click Content for AdSense for content.
4. Click Manage Ad networks.
... (ETC., ETC., ETC) ...
To allow or block new Google certified ad networks:
At the top of the page, click the control to indicate whether you'd like to automatically allow or block ads from ad networks that are certified by Google in the future. This includes only ad networks that may be certified by Google in the future, not ad networks that are already certified.
To allow or block current Google certified ad networks:
Click the control next to the ad network name to allow or block it.

I HAVE NO "Manage Ad Networks" option. It simply isn't there.
My content options are -
- Ad Review Center
- All sites
- www mysite
- mysite

.

After an hour, I finally stumbled my way into a "Manage Ad Networks" page.
I could NOT find a global command to activate ALL.
As if I am going to do 5,000, one-at-a-time. Not.
LOTS of other ways to waste my time, which I KNOW are more productive. Sheesh.
.

Hello,

Indeed, it's not longer possible to block all or allow all, you have to manually do it for EACH ad network ! In the past, there was the option to check or uncheck all. I don't know why the removed it. The worse is that, when you do it manually, after tens of them, it's starting to take few seconds each time you click the radio button before you can do the next !

By the way, I allowed all ad networks, but I did removed all networks with the name being like "don't use", "old", etc...

NickMNS, do you block any ads or just let them all run? I'm wondering if I'm blocking too many. If I unblock them and it turns out to make no difference with revenue, then I have to block them all over again, because I can't stand to look at them, which is a tedious pain. I let all of the ad networks run for the reasons you state above.

@ember,
I have basically given up. I used to spend time each day going through ad-review and blocking all the crap, but it is a loosing battle. Ad-balancer helped in that regard, in that you could essentially remove any "unsold" inventory (reducing supply at the same time as reducing demand), but now that is gone too. So I'm done. Whatever ad wins the auction, gets displayed. Given the insane variability from day to day in terms of RPM, it is essentially impossible to measure whether or not blocking or not has any real impact on revenue. But not blocking has the benefit of providing me an extra hour a day not wasted on blocking AdSense spam and instead putting that time to working on projects that make money without AdSense.

@Sally Stitts

How long should I wait before reporting my new results here.

As I mentioned above, when it comes to Adsense (at least in my experience) there is so much variability, not just with AdSense itself, but also other factors such as changes to the SEPRs, that it becomes really difficult, if not impossible, to attribute a change in revenue to any one specific action.

Given the insane variability from day to day in terms of RPM

Isn't that the truth. One day looks normal, the next day the RPM is half that and the next day it is three times the first day. Same traffic as always. I chalk it up to the virus because it makes as much sense as anything else.

Sorry, been busy as heck. OK. Thank you folks for shining light on the situation.
My path is now as clear as a window pane. Fugitaboutit. You have saved me hours and hours of searching, wondering and cursing.

THAT'S WHAT I LOVE ABOUT THIS PLACE.
"Money for nothing and the chicks for free", or, "Knowledge for nothing and the advice for free".