What: Facebook just released a major upgrade to its social plugin that enables user commenting on a site, including such new features as threaded comments, moderation control and the ability to sync comments from a blog to a Facebook Page.

How It Impacts Marketing: Hubspot gives a good overview on that subject here. Essentially the upgraded plugin is a mixed bag for marketers, it says, as it provides innovation for blog comments but at the sacrifice of some control. This plugin effectively hands over over the commenting function to Facebook.

Where it Excels: It encourages engagement while allowing businesses to build Facebook reach, Hubspot says. "Every time a user posts a comment using Facebook's commenting tool, they have the option to also share that comment on their Facebook Wall. If users adopt this feature, this will be a big potential reach builder for businesses."

What Else: The plugin displays the most relevant comments from a user’s friends at the top of the section. It also syncs comments from a blog post and Facebook page.

The Big Picture: The plugin, plus Facebook's acquisition of Beluga are key parts of Facebook’s unified inbox strategy, and its attempts to become an integral part of how we communicate with each other online, writes GigaOm. Text messages, SMS, chat conversations or email all are funneled into a single location where users can see their ongoing conversations regardless of the method used.