We've all gotten used to to those Facebook email notifications - you know, the ones you forgot to disable when you originally signed up for Facebook, and began to receive in larger and larger quantities as more and more of your friends joined Facebook, until you finally broke down and navigated through the jungle that is Facebook's account settings and disabled.

Well, you might want to consider re-enabling Facebook email notifications, because they just got a lot more powerful today after Facebook announced that you can now reply to notifications via email and have those replies pushed out to the Facebook thread you received the notification for. It might not sound like a big step but it represents a fundamental shift in Facebook's attitudes toward bringing more traffic to the world's largest social network - a shift from "traffic is the key" to "engagement is the key."

In a Facebook blog post today (Replying to Comments through Email) Facebook made the announcement that users can now simply hit "reply" from their email or webmail client, type their message, hit "send" and have that reply show up on Facebook - without the user ever actually needing to login.

One GREAT usage of this new feature is to enable users who work in an office environment where Facebook has been blocked to continue to engage in the social network, even though they can't actually visit the Facebook website during working hours. With more and more companies out there going after workers who use social networking while on the company dime, this feature is sure to create a stir in the corporate world and increase the amount of replies showing up on Facebook during normal business hours.

More importantly, though, this reflects a change in Facebook's attitude. Previously, if you wanted to reply to a comment, you had to log into Facebook - which is exactly what Facebook wanted. Their business model depended on you actually visiting the site, so they could hit you with advertising and hold up their monthly traffic as an indicator of how strong the social network is. Now, though, Facebook is shifting away from a purely traffic-motivated model and more toward a model that rewards and encourages user engagement. Facebook wants you to use Facebook more, even if you're not doing it through their website, because they recognize that the more YOU use Facebook, the more your friends are going too use Facebook (and, by extension, the more THEIR friends are going to use Facebook).

Keeping users engaged and having conversations is crucial if the social network hopes to sustain the massive growth it's experienced over the last few years. With more and more people using Facebook, eventually they're going to start experiencing diminishing returns when it comes to new users - essentially, there will come a time when the market is saturated and everybody who's going to use Facebook is already using it. Although that day is still many years away, Facebook clearly recognizes that it's coming, and their plan is to try to squeeze more activity out of the users they already have rather than only try to bring in new ones. If that means sacrificing a little traffic to the domain so that they can get more replies and activity out of their users, that's a decision they're willing to make - and it's a good one.

It's refreshing to see Facebook actually looking farther into the future than a couple of months. The response to the new feature is overwhelmingly positive, with many users wondering why Facebook didn't do it already. The answer, of course, is that they could have enabled this feature at any time - reply by email is nothing new - they were simply waiting for the right moment, and that moment, it would seem, has arrived.