Facebook appears to be rolling out functionality that allows users to reply to updates on the site from their email account, simply by hitting "reply" and typing the message you want to reply with.
It's a simple step, but one which social networks are often reluctant to take as they rely on selling a huge number of page impressions to advertisers - something which is harmed considerably by allowing people to reply to messages from other sites.
But it seems like Facebook is really committed to opening up its walled garden. The next step will be to allow users to reply to Facebook mail in the same way - that can't be far off if this is rolling out now.
The functionality seems to be being slowly enabled for all users, but it doesn't seem to be live for everyone yet. Let us know in the comments whether you have it yet and what you think of the functionality.