When you say you're not seeing a lot of engagement with FB/Livefyre, were those sites seeing engagement before with a worse commenting system?

We switched ForeignPolicy.com over to livefyre from the Drupal built-in system and saw a big increase in participation, both in average comments per article and the number of multi-message 'conversations' that people were having in the comments section. That said, we already have an engaged audience, and a big chunk of the benefit may have been new moderation tools that let us reduce spam/trolls.

I don't think that any system will create engagement out of thin air, except in the rare case of a site with a rabid fan base and no commenting/forum system, but i'd argue that systems like disqus and livefyre make people more likely to jump in because they don't need to create an account with you.