The material facts of a listing on Craigslist don't belong to Craigslist. You can't copyright the fact that a given listing is for $2400 a month. You can't copyright that it's at a given street and cross-street and the number of bedrooms and bathrooms on the premises. I don't even think anyone should copyright the aggregate of the above data. To do so would be evil. (In that there would be widespread implications.)
It's not their data. It's their listing. Those are two different things.
Are you saying that Craigslist doesn't own the data, but it still owns the aggregation of the data?