Update - Facebook Messenger for Windows launched, Mac version comingFacebook Messenger for Windows leaked, Facebook has released the official desktop client. Facebook contacted me and said the official Messenger for Windows download link is available from fbcdn_dragon-a.akamaihd.net.
Facebook would not confirm the version number with me (update: I figured out it's version 2.0.4373.0), but given that the application updates automatically, I think Menlo Park made a decision to officially release it instead of trying to combat the leak. Smart move. This means that the screenshots I put together earlier today still apply: Facebook Messenger for Windows leaks (screenshots).
Facebook started testing the Messenger for Windows desktop client with a limited group of users last month. The application, which requires Windows 7, provides access to three main Facebook features: Facebook Chat, the new Ticker feed, and notifications. In addition to Windows 7, Facebook Messenger is also already available for Android, iPhone, and BlackBerry.
Facebook has hinted at a few upcoming features for the Windows flavor already: chatting with multiple friends, video calling, limiting chat availability, and editing settings. It's not clear if the company will be making announcements for every new version or if they will be just quietly released like this first version.
So, what does this application require to keep you updated? First and foremost, you must be logged into Facebook. After you click on the blue "Log In" button pictured above, you will redirected to the facebook.com/desktop/login webpage where Facebook explains that Messenger for Windows requires you stay logged in so that it can deliver chat and notification messages to your desktop. This means you will stay logged into Facebook even after you close your browser. To log out of Facebook, you'll need to actually do so from Facebook Messenger for Windows.
Facebook believes users want to use the social network's real-time features without having to keep a browser window open. The social networking giant is clearly hoping that users will leave Messenger for Windows on throughout the day, probably since most Facebook addicts already do so with a browser tab. In addition to being a standalone application, Facebook Messenger for Windows can be snapped to the side of the screen; that's probably why it only works for Windows 7.
The application was developed entirely by Facebook and does not constitute a new partnership with Microsoft, which is a big investor in Facebook. It's not clear if Facebook will offer support for anything before Windows 7, or if it will simply move on towards Windows 8. Clients for Mac and Linux will likely only be released if the Windows 7 version proves popular.
Update - Facebook Messenger for Windows launched, Mac version coming