What's the source of your belief? Just a guess based on your common sense? I'm curious. I still think they should add the feature.
LOL. It's not a belief; it's a fact. Anything that creates a danger of injury creates a risk of liability. For both freecycle & craigslist, the risk to users would be much smaller because people do not share details about their children or their family lives on those websites. In fact, the risk of using those websites is equivalent to the risk of having a pizza delivered. It's clearly different to disclose the intimate details both of one's family life and of one's residence.
My source? Personal experience. I'm a lawyer.

I can tell you that the area of website liability is still largely untested. The extent that websites will be liable when their users suffer an injury has yet to be decided (and will depend on the jurisdiction, the judge, etc.).