There are many more solutions that are just as easy (and have better returns). Adsense is no longer the only place to go for ad placement.
I'm presuming this is because the good ad networks don't need to look for sites to display on, but I haven't found anything else that's as good as AdSense. (And due to TOS, we can't run AdSense.)
The network ran trials of using Google ads on certain pages, and some did OK $10k per page per month (on popular pages). But at the end of the day that barely covers costs of running the network.
Google can't supply the cross medium advertising either, so most agencies are more than happy to pay the extra $24.60/cpm to actually get to the desired markets. The old saying "you get what you pay for" really sums it up really.