Marketplace did not yet take over local sites, but it's getting there for a lot of people. They hated having to move off facebook to some 'inconvenient site' (yes, indeed, many people find sites other than Facebook & Whatsapp very inconvenient to work with) to sell their stuff, while now it's an easy experience for them. I see it growing rapidly every day where I live (south of Spain). Considering many people are born into Facebook (the first (and often only) device they (will ever) own is a smartphone and that they use for Facebook and Whatsapp), it is very natural that many people just stay in that eco system and prefer never to leave because it's so convenient.

Dating might be seen as a bit too much though; many people (for whatever reasons they have for it) prefer to keep their dating life away from their normal interactions. It depends on how it works, but it seems unlikely it will be seperated from the normal experience which I think will be a big hurdle for many. Then again, maybe it's already known and fixed as this is the first time I read about it.