Edgeio will spider and index anyone’s feed and aggregate the posts tagged with “listing”. It then clusters the other tags in order to attach the post to the right classifieds category. The revolutionary thing here is that Edgeio does not require you to post your offer on their own site, they go and take it from yours..
Forgive me for being pedantic but this is not edge aggregation - it's centralized aggregation of content from the edges. But not to the edges . Its no different to centralized RSS readers like Bloglines and Rojo, or memetrackers like Tailrank and Memeorandum, all pulling in information from Blogs and presenting it centrally.
True Edge Aggregation requires distributed aggregation to the edges ie. back to the blogs. And one way we'll do that is with feed grazer widgets like Grazr, OPod and OptimalBrowser, which are already popping up in numerous blogs.
Tom Raftery took Edgeio for a spin by advertising a Nissan Micra and an Antique Italian Cabinet for sale. He included the tag Listing in both posts to ping Edgeio. I hope Tom doesn't mind but I've now added them to the Open Irish Directory bookmarking service by clicking on the OID Bookmarklet (just drag it to your toolbar) and using the same tag - Listing. It took all of 5 seconds. All bookmarked posts with the tag Listing are now being aggregated to the OID (see Grazr panel in sidebar) under the hierarchy
Leisure & Sport -> Shopping -> Classifieds & Auctions 
Now that's true Edge Aggregation - from the edges and back to the edges. I have to say I'm a great admirer of Mike Arrington and what he's accomplished with TechCrunch but I just don't see how Edgeio is defensible when all the pieces of this jigsaw are already out there and, as Matt Terenzio observes the trend is toward distributed models superceding centralized marketplaces.
 In fairness to Edgeio their tagline is Listings from the Edge so its the commentators rather than the company themselves who've been perpetuating the misnomer.
 'Classifieds & Auctions' is an individual OPML node so if you don't like it in that position in the hierarchy you can easily place it where you like on your own Grazer. That's the magic of OPML.