Crowdsourcing and Big Data and a rating/flagging system.
I don't need to know Sergey Brin to be able to post an ad on Google. It is an automated process. I don't know Morgan Freeman, I mean Meg Whitman, although I believe I do follow Pierre Omidyar on Twitter ("Can you like tweet back once in a while, Omidi?") but I can list items on eBay just fine.
Zady runs the risk of ending up interesting and small. But it has the potential to be really big. And big is when you make it easy for people to get on the Zady train. I hope the startup has a great CTO who will put the brains to carve out a great tech solution to the scaling issue.