The old marketplace wasn't structured probably. Private groups centered around cities rather than through friends is the biggest change.

The social proof that FB allow for, make it possible to sell to people you don't know much more securely.

It was one of those things that the community itself developed and FB just turned it into a service.

I was considering getting into this space a few years back but realized that FB would eventually catch up.

Still is room for non-fb competitors but their social proof card is hard to beat IMO.