I've been thinking about advertising in RSS for a while (and Google's foray most specifically) and always with a general distaste for it. It wasn't until recently that I was able to put my finger on exactly why I think it's misguided, but I think I figured it out. From my experiences in using Adsense nearly two years on PVRblog, I've noticed a great deal of my traffic comes from search engines. I only have stats on those viewing the site via the web (bloglines says 4k users read it via RSS, but there's no way of knowing the full number), but a random swath of stats will frequently show 75% or more of the web traffic has google.com as their referrer. Here's a screenshot of my Typepad stats, showing a single page of accesses in the past few minutes as I'm writing this. The ones with no referrer listed were reading the site directly. These are folks looking for information on products I reviewed and mentioned or tips I might have divulged in a post. I have no way of verifying this, but I would assume that my adsense click-throughs are mostly due to this search engine traffic and not due to my daily readers. At the very least, the random searchers simply outnumber the daily readers, but I think it goes beyond that (which would assume both groups click through ads at the same click through rate). I don't have any data to prove this, but I'm going off on a hunch since that's how I tend to use google's text ads myself. If I'm searching for information about a baby monitor or trying to figure out when the superbowl is starting, and I end up on a site with Google text ads, I often click on the ones that seem to offer better info than the site I'm viewing. If I'm viewing a page that mentions the text string "Superbowl" and "start" and "time" but doesn't answer my question, and there's an ad that says "Plan your Superbowl Party Here" I would probably click it, hoping they happen to mention the kickoff time. Let me circle this back to ads in RSS feeds. You can be fairly sure that every single person subscribed to your feed is a daily reader and it's not likely random searchers would add your feed. The people reading your feed are using a feed because they don't want to miss a single word you're saying. They're not just fans reading your site, they're more die-hard than that. Who would you subject to advertising, if you had a say in the matter: random visitors or your biggest fans? I've come to the conclusion that I do have a say in the matter, and that I do my best to decrease advertising pitches to my biggest fans. On MetaFilter for instance, there are blogads and google text ads for outside browsers, but when you get an account there you don't see any of it and the site is ad-free. PVRblog has both blogads and google text ads on the site but I won't be adding anything to the feeds. None of this is set in stone, of course. Currently, the technology that does text matching in all the RSS ad examples I've seen is quite poor. Out of the context of a site with thousands of words, giving a unique ad to every single post that might only have a handful of words seems to result in totally random ads. I find myself looking at a someone's blog post on iPods and seeing a text ad for refinancing a mortgage far too often. If ads in RSS were more sophisticated and actually were pitched at the very things you were discussing in a post, I might reconsider. The other main thing that might change over time is that RSS readers are typically technology-savvy and a small minority of your audience. If RSS grows to the point that random visitors become the majority of your traffic, it might be time to reconsider this, but for now it seems pretty obvious: don't clobber your biggest fans with pitches to ads and instead relegate ads to areas where it might help people find more information or related products.