Pros: Requiring comments via Facebook means loss of anonymity.
I suppose it depends on what your priorities are. If you'd like the insightful input of someone who might be close to the source of the topic at hand, but maintains anonymity for safety or fear of repercussion, then the requirement to use Facebook could be quite damaging.
On the other hand, if your primary concern is the nameless faces spewing hateful, racist, or otherwise inflammatory garbage on your comments section, the Facebook requirement with its real-name policy could go some ways to curtailing that kind of dialogue.
I imagine your average article discussion consists of 5% of the former and 95% of the latter, and so I can understand why they might choose to go this way, even if I am disappointed by it.