I was thinking how do you start a site like Backpage (or Craig's List). I mean day one there are no ads and no one knows it is there. Or opening a new city (I suppose you could grab all the ads from neighboring areas that are actually from this city).

These sites are different because they are regional. It makes no sense to market a prostitute three states over.

Just musing. I am neither implying anything sinister or fishing for ways to start my own such site.