@iamlost
I agree with what you said but I feel a few important clarifications are necessary.
The problem with an average, of course, is that half of the values calculated from are below the average.
No, what you describe is the median. The median is the value for which 50% of the distribution is above and below. While it is often true that the median and and the mean (average) are equal, there are many situation where this is not the case. This is what describes a skewed distributions. When discussing Ad revenue the distribution is definitely skewed. That is few publishers earn a high RPM and many earn low RPM. The distribution has a long-tail (don't get me started on long-tails!).
The implication of misconception he is as follows, for example that a few publishers are earning $20RPM and we are told that the average is $2RPM be I earn $1.75RPM and thus feel like a chump because most publishers are doing better than me. This because I assume that the average and median are the same but they are not. If one looks at the median it is a $1.50 so I am actually in 75th percentile and thus doing better then most.
I realize that this distinction does not really change the gist of your argument but I feel it is an important distinction to highlight because many people are often confused and mislead by these types nuances. My long-tail pet peeve is a perfect example of this.
while ad retargeting means that niche is less important,
I think what you are describing here is interest based ad targeting and not specifically retargeting. Retargeting is when a user has visited a site and then left and then that website uses ads in combination with cookies to serve ads to that user in hope of luring them back to website to complete a transaction. My understanding was that these types of ads can have a high payout given that the advertiser has a big incentive to regain the customer (I may be wrong). Interest based targeting is more general, users are simply targeted based on browsing history and other indicators. In this case earning are likely lower than contextual targeting. Retargeting tends to occur less frequently. Whereas interest based targeting can consume a large portion of all impressions. This is specially true if there is low demand for contextual ads on you site.
You can see how your site fares in AdSense by going to Performance Reports => Advanced Reports => Targeting Type. The "Personalized" category covers contextual ads and I assume retargeting. As I do not see any specific reporting for retargeting type ads.
