[magduf]

If I'm buying a used piece of furniture or whatever, I don't give a shit about prostitution going on elsewhere on the site.

What's really hurt Craigslist is all the scammers. You can't post anything of value on there without some scammer responding and telling you they're going to send you a cashier's check and have a personal assistant pick it up.

You don't have this problem at all on Facebook AFAICT. When someone responds to your ad on Facebook Marketplace, it's a real person who actually wants to buy your old junk.

[Spooky23]

The scammers aren’t there because of prostitution, both categories are there because Craigslist attracts unsavory parties and does little or nothing to police them.

[magduf]

No, that's not correct at all. The difference is that Craigslist has no real accounts. When you get a response to your CL ad, even if the responder has a CL account, you don't see this, you just get a text message or phone call or email. With FB, everything is through the site because of the way it's centralized, and you can see the account and full name of the person who's contacting you. On CL, it's trivial for scammers to respond to ads with automated programs, but on FB they'd have to create a real-looking fake account in your area, complete with pictures, some kind of history, etc., which is a far greater undertaking.

In short, the formats of the sites make all the difference. CL was created to preserve anonymity and not be a centralized social network, but that feature is also its undoing because it facilitates scamming.