As RSS moves more mainstream, measurement problems are arising around how to incorporate RSS click throughs into clickstream analysis products like Omniture (SiteCatalyst), WebSideStory, Coremetrics, and ClickTracks.
Right now there is no way to get a complete picture of how many people are viewing a particular piece of content or an ad except by taking performance metrics provided by various siloed products and aggregating them by hand. This will work if you have a small number of feeds, sites, and discrete bits of contents and ads to track but obviously won’t scale for publishers and advertisers who are tasked with tracking hundreds or thousands of pieces of content. Expect the problem to get worse before it gets better as more in-context advertising opportunities are made available to advertisers.