After some resistance I made the switch from a downloadable RSS reader to Google Reader. Two weeks later I’m totally addicted and my pageviews to my “regular reads” websites has dwindled to near zero. No problem for them, you say, RSS ads can solve their revenue problems.
Um no. RSS ads are untargeted, static, unengaging, crap. Below are some articles from my Reader account that include RSS ads…
The ad below appeared something like 20 times. You can’t frequency cap when you aren’t dynamically serving anything.

Well, at least from the ad below we know that HP is varying the copy a little. Still very untargeted, essentially the advertiser is buying a “tech” audience (no duh, it’s RSS). They can’t even tell if I’m in the United States or somewhere the products aren’t sold since Reader is the only one who knows that information.

OK, below we finally have an example with some graphics. But I can’t interact other than a click (Flash not supported easily). I can’t calculate reach and frequency. And targeting still sucks.

In order for RSS ads to be meaningful there are two opportunities:
1. The content providers need to sell ads themselves, based on more detailed audience and content targeting. By deeply integrating into their own content management systems the publishers can better make the ads relevant. This won’t overcome the interactivity or geographic problems, but it will be a start.
2. Aggregators like Google (owner of Feedburner) can embed better quality display ads and utilize better targeting since they have access to the user at the time of reading. This would require scale since agreements would need to be made with the fragmented content providers. At this point only Google has that scale and the necessary properties, but that could change.
Full disclosure: I work for a company that has an agreement to be acquired by Google.