I did not see it replacing KHF to be honest. It was more a way of letting those members stay in touch with each other who want to. Since you can post photos in facebook, it could also provide a Guess The Place equivalent, if enough people wanting to continue playing were to join up.
It is not the best platform to post and categorise and record historic information. There is nothing stopping people making posts with information like on KHF if you want to, and of course, people could reply and add info and comment. It would just not be indexed and categorised. There is a facebook group search if data was to be added and people wanted to find specifics