Online classifieds service edgeio just launched. I tested the service out recently, so here are my thoughts. Firstly I should make the disclaimer that edgeio co-founder Mike Arrington is a friend and I also know Keith Teare. So my opinion on this matter is undoubtedly biased.
I love the concept of edgeio, because it's almost exactly The challenge for edgeio will be getting bloggers to post listings the same ideal as the Structured Blogging initiative. Structured blogging means publishing different kinds of information - like events, reviews and classified ads - in a 'structured' format, so that aggregators can pick up the data from all over the Web. In fact, at the bottom of the structuredBlogging.org homepage is a pretty good description of what edgeio does!
"Now anyone can build applications or services based on the structure of an entry. Using Structured Blogging, [...] buyers and sellers of goods can publish what they want to buy or sell and have those posts searched and listed by any number of search services."
Replace "any number of search services" with the word "edgeio" - that's what edgeio is about.
edgeio gathers goods and services data by scanning over 25 million RSS feeds, looking for the tag "listings". It also has a set of APIs. The search and filtering system for users looking for items to buy is very well designed and has some clever touches. For example, if you type "ipod" into the search box it brings up a results listing which you can filter by date or price. But you can also add tags to further filter results - e.g. click the "video" tag if you're actually after the video ipod. Voila, that filters down the many 'ipod' results to the following single one:
You can also filter by geography. All in all, the design is very slick and easy to navigate. Edgeio also has good alerting mechanisms for clearing out all the spam that will inevitably flow into the system.
The real challenge for edgeio will be in getting bloggers to post listings, not to mention there are a lot of people still without blogs in this day and age (shocking, I know...). This is also the big challenge for Structured Blogging. In fact edgeio will soon (within a week or two) be releasing plugins for both Movable Type and Wordpress, just as Structured Blogging did. So that will help get people to post listings on their sites.
Incidentally there's no reason why edgeio and the open standards fueled Structured Blogging can't co-exist in the same ecosystem. edgeio is an aggregator, so they will want to gather data from as many sources as possible.