The notion of what's happening in the feed "marketplace" is interesting to lots of folks. The headlines this past week have all been about Google Reader dominating and other readers/aggregators receding. A while back it was that Bloglines was King of the Hill. Whatever grabs headlines on TechMeme is what a lot of bloggers will write about. Today, FeedBurner put out a piece that sizes up the Feed Market and begins to introduce a new concept: Engagement. At the end of the day, subscriber numbers aren't that interesting to a publisher. They want, nay, NEED to know what's actually happening with their content and a way to measure their audience engagment whereever it is happening. It's an exciting time at FeedBurner as things are getting rolled out fast, but we'll continue to come back to the concept of "engagement", as we think that's the most important metric not only to publishers, but also to advertisers.