I am going to take this with a grain of salt...while this might be the first wave of novelty-wearing-off, it is not necessarily such a bad thing. The experimentation on the RSS advertising side has not even fully begun.
Anyway, a study by RSS ad vendor Pheedo shows that the average CTR of “standalone" RSS ads is 2.76 percent, while “inline” RSS ads, or ads within an individual feed post, are getting a .45 percent CTR. In the same study five month ago, RSS ads grabbed an average 7.99 percent CTR and inline feed ads got a .85 percent CTR on average. In the new study, these rates dropped 65 percent and 47 percent, respectively. The company believes that feed ad CTR will continue to normalize, and the decline rate will taper off.
Ad frequency is a factor...inline ad in every post is a bad idea...Feed content itself had an impact on ad CTR, too, according to the report. Ads placed within Comics and Humor; Travel; and Kids and Family feed content verticals spurred the most average CTR at 9.62 percent, 8.54 percent and 7.61 percent, respectively. Games; Arts and Literature; and Sports and Recreation came in at over 4 percent, while Politics and Consumer Technology got an average CTR of less than 1.5 percent.
Also, summary feeds got a median CTR of 8 percent, while full feeds garnered a 10 percent median rate.
Full study report here