I'm speaking on a panel on Web 2.0: Tools for Creating a Community with Jeff Clavier, Laura Merling, Kevin Rose at the eBay Developer conference. Lots to talk about. And talk has always been (de)central for eBay, as I noted when they bought Skype.
Pierre Omidyar once explained to me that one of the smartest things he did when starting eBay was to not constrain communication around his market -- by publishing email addresses. He was suggesting to me that we open the Socialtext Customer Exchange, but the core insight is more valuable. Back when I was running a B2B exchange, this was considered a contrarian move. After all, it let buyers and sellers circumvent your transaction fees in some cases. But letting go of control fosters liquidity. Especially when you couldn't possibly structure communications to fit all transactions. Today I would venture that most of the communication on eBay's transactions are out-of-band. Other communities with emergent liquidity such as Craigslist succeed by enabling even further out-of-band communication.
But there are some unique challenges for eBay's next generation community. Principally, while markets are conversations, social software gets spammed. And while eBay desired a fact-oriented wiki, it both inherets community values and doesn't have the luxury of cultivating it over time once the wiki is made public to the masses. I've chatted with eBay about blogs and wikis since the Omidyar Network investment, and these folks get community. But the social contract seems borrowed from Wikipedia and it will be interesting to see it be rewritten.