Facebook just sent shockwaves through the social web with its announcement that they will be supporting @mentions in status updates. The feature, which Facebook calls tagging, allows you to not only reference friends, but groups, pages, and events.

Without any hesitation we will say that this move is a direct attack on its upstart competitor Twitter, whose @mention feature (formerly known as @reply) has been an integral part of the microblogging service. This is only in addition to a wave of other recent moves by Facebook to halt Twitter in its tracks. Real-time search and the FriendFeed acquisition were just the beginning.

This move has more direct impact on Twitter though, especially as many Facebook users utilize Twitter as their status update tool. Here are some of the likely implications of Facebook's new feature:

1. More of the conversation moves to Facebook: This one's inevitable. With the ability to tag and chat with friends in public, some of the public conversation that has been for so long on Twitter will migrate over to the larger user base that is Facebook. 2. Users could update Twitter through Facebook instead of vice versa: Soon you could see people updating Twitter via Facebook, now that you can reference people with the same syntax. Facebook recently launched a Twitter app for Pages. If it were activated for profiles, user habits would quickly change.



3. Facebook becomes more attractive to big brands: Now brands can reach out to users complaining about their brand as well. And since Facebook is bigger, there are more customers to serve. It adds a whole new level of interaction between brand and user.



4. People move to Facebook for breaking events: When there is a plane crash, an earthquake, or a conference, people tend to turn towards Twitter first. With @mentions generating conversation, it makes just as much sense to update on Facebook. This could accelerate as the platform becomes more open.



5. Developers flock back to Facebook: What makes sense for Tweetdeck: serving 10 million Twitter users or 250 million Facebook users? As more and more of Twitter's functionality makes its way onto Facebook, developers can build fully-functional apps for accessing Facebook and utilizing its data. It could be a renaissance for the Facebook platform.



While it's way too early to understand the impact of Facebook @mentions on Twitter, it seems clear that its impact will be big. You can't just take one of Twitter's best features and adopt it on a platform several magnitudes larger and not see an impact.

Now we want to know what you think. How will this change impact Twitter? What about Facebook? Do you think we'll see a seismic shift or will this just be a blip on Twitter's radar?

[Image via Flickr, mariachily]