(In at least a few foras I frequent the result is that in most controversial case you miss out a whole lot of reasonable but not politically correct voices. Real trolls either don't care about Terms and Conditions and create another fake account or they troll using full name and address.)
http://www.huffingtonpost.com/otto-toth/were-moving-the-conv...
There are some self-hosted systems out there, including my trivial e-comments code: https://github.com/skx/e-comments/
I remember a few years ago whenever you clicked on a Guardian news link in Facebook it would try and get you to sign up to their Facebook app/plugin, that would then publish on your timeline what you'd been reading, let alone commenting on. I thought that was a bit ghastly.
I'm assuming that when you make a comment through Facebook on the Huff post, it displays on your timeline or some such, providing additional reach for the story.
Some cloud services are used because they're actually useful and good at what they do.