Pros

• Real names and identities greatly reduces the number of trolls and anonymous cowards in comments.
• Social virality boosts traffic by creating a feedback loop between Facebook and participating sites.  Friends pull in their friends, creating a social entry point to your site.
• Automatic sign-in if you already signed into Facebook elsewhere, lowers the barriers to commenting.
• Most “liked” comments get voted to the top.  It also knows who your friends are, so you will see those comments first.

Cons

• No support for Twitter or Google IDs, which leaves out the other half of the social Web.
• No backups and other lock-ins will make it hard for sites to leave.
• If you work somewhere that blocks Facebook, you are out of luck.
• Your friends might be surprised to find their replies in your Facebook News stream reproduced on another site’s comments.  Expect a backlash.
• Moderation bugs, no view counts at the top of posts or ways to highlight site owners/writers in comments.

What do you think are the biggest pros and cons?

This is a good discussion of the new Facebook commenting system. I fear I will eventually (and perhaps sooner than later) be switching over to them. The issue is that because I write about topics that people worry about which people worry about expressing their opinions openly, it could hurt the site to use a system that requires them to log in with a real identity.

The question is whether that's worth it. It also reduces spam comments, which continues to be an issue. So I'll continue to look at the positives and negatives.

Any thoughts are welcome. ::