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A little more digging into this story reveals that the Facebook Classifieds service, first rumored by Mashable, is now live and powered by Oodle.
Oodle just went launched this Facebook group, which lets you post an ad and distribute it via Facebook Share - a smart integration that will let all your friends know when you are selling something. However, it seems to me that the service is built on the Facebook API, so Oodle was given a similar toolset to all the small, independent classifieds sites that sprung up on the API. Textbooks, tickets and residential listings seem to dominate the listings. Listings are free and created over on Oodle's site.
Another tip you heard here first: Friendster is also launching a classifieds service tomorrow.