I find Facebook's format bizarre and clumsy. It's hard to find a comment more than once, it keeps randomly defaulting to "Top Stories" no matter how many times you set it to "Most Recent," it's a crapshoot whether a comment you post will actually reach everyone to begin with... it's horrible. I don't understand why people like it.
My issue is less with the format than with how incredibly negative and cynical most of the commenters on FB seem to be, trashing just about everything in sight.
It's not quite as ugly and nasty as the Youtube comment section just yet, but it's definitely getting there.