It is a good idea - and it belongs in the Classifieds section.
Doing it this way requires that I "police" every post where someone asks to buy or sell beans outside that single post, point them to the correct post, and close down the one where the question is asked (unless it's a blog in which case there's nothing I can do).
I mention that because we tried to create a single "official bean-to-bar chocolate maker" thread and in the end it turned out to be too much work to force all new entries into the single "official" thread.
Blog/discussion software is not the best tool to this. If anyone has some programming skills and wants to work on some useful database tools I would be happy to work on this.
clay - http://www.thechocolatelife.com/clay/