Craigslist knows there are are lot of scams and so when you go to contact a seller they give a big warning that there are scams and so avoid them. Facebook accepts ad from scammers but gives you no warning that they do that. And not just things that marketplace, but they also accept ads from scammers and redirect you do their website for the scam - without any warning that it could be a scam.

I refuse to buy from Facebook because they mix things so that things that it seems I shouldn't have to beware of could be scams. I don't mind buying from a potential scammer - but I'll take extra action if I have reason to worry, which in turn means if you are not local to me I won't buy from you. There are a lot of things that I cannot get locally though, so I have to buy from someone who might or might not be scamming me, there I look for signs that it is not a scam - and there Facebook is not helpful in separating out scams from legitimate companies.