Let me start by just saying I LOVE WIKI! Wiki is a site (or portion of one) that allows everybody and anybody to edit any page. It initially sounds like havoc but with multiple copies of a document being saved, so that there is a way to rollback, and by having strong community ties, it actually works out great.
EBay’s new Wiki (at eBayWiki.com) is the biggest “commercial” Wiki out there. Wikipedia is bigger but is not for profit. EBay’s actual Wiki does not bring in direct profit, unless they plan on putting ads on it. It is free for all eBay users and is meant to build up the eBay community.
I envision eBay’s wiki being a mix between a forum, Wikipedia and Digg.com. Most of the articles are going to be in a category such as “Antiques”, “Art” etc… The more popular articles, like Digg, will bubble up to the top. The main idea is that these articles will have tips to maximize your eBay profits from selling, or find items that you are looking for. This along with building a huge amount of eBay brand loyalty equates to $$$$ for eBay. EBay also announced that it will start serving ads like Google so expect ads on the site which will more than likely be tastefully placed.