I built http://bidwars.net (try http://pittmaplemiss.bidwars.net/ for an active group). It's currently for sale on Flippa and the auction has more details: https://flippa.com/2944217-craigslist-competitor-with-14-700...
Summary: It's the love child of eBay, Craigslist, and Facebook. 7,200 users since January 2013. Currently making around $550/m in AdSense revenue. Growth has stabilized. Roughly 20,000 pageviews a day from 3k visitors.
Stack: LAMP + CodeIgniter, Saas, Coffeescript and jQuery.
skype: gr33nw00d, email: dr.greenwood@gmail.com