Network effects. Brand/mindshare. One pattern that you could apply to break craigslist would be focus: http://ycombinator.com/munger.html http://ycombinator.co

Network effects. Brand/mindshare. One pattern that you could apply to break craigslist would be focus: http://ycombinator.com/munger.html http://ycombinator.com/munger.html [Search for 'travel magazine']. You'd want to pick a suitable niche within craigslist and service that like crazy. Then move on to others.