Facebook has done it again - weeks after it joined hands with Skype to beat Google+ Hangouts, the world's No.1 social networking site has launched Facebook Messenger, a free mobile app for iPhone and Android users that allows them to send and receive real-time messages from their Facebook contacts.

The app, which was launched on Tuesday, is the first dedicated app released by Facebook. There is already a general purpose Facebook app for mobile devices that allows one to sign into the site.

According to a Facebook blog post, Facebook Messenger is a "modern messaging system" as "All your conversations are in one place, including your texts, chats, emails and messages."

"Whether you're on your phone or on the web, you can see the full history of all your messages," Facebook said.

Moreover, Facebook Messenger makes sure that the person you have sent the message to has actually received and read the message. "More and more of us rely on our phones to send and receive messages. But it isn't always easy to know the best way to reach someone on their phone. Should you send an email or text? Which will they check first? Did they even get your last message?" Facebook said.

"We think messaging should be easier than that" and with Facebook Messenger "You should be able to write a message, click 'Send' and know that you will reach the person right away," the company said.

"More and more of us rely on our phones to send and receive messages. But it isn't always easy to know the best way to reach someone on their phone. Should you send an email or text? Which will they check first? Did they even get your last message?" Facebook said in a blog post. "We think messaging should be easier than that."

The Facebook Messenger app, developed by Beluga, a group text messaging service acquired by Facebook in March, is set to become very popular as it aggregates texts, chats, emails and message history all in one place — synced across mobile and web - and can also send out messages, which supports attachments and location information, to groups or individuals.

The Facebook Messenger is easy to use. The user just needs to log into the Messenger app using his/her Facebook user id/password and then they'll be taken to a screen with all of their recent Facebook chats and messages which can be displayed as a message thread and the message thread can even be given a name for easy grouping and tracking.

A nifty feature of Facebook Messenger is that you can use the app to send IMs to anyone you want i.e. your communication is not restricted to only Facebook users. Once you have typed out the message, you can draw contacts from both your Facebook friends list and your phone's address book and while messages to Facebook friends will obviously be sent via Facebook Messages, messages to phone contacts who aren’t on Facebook will be sent via SMS. In other words, nobody misses out in the fun. However, it makes better sense to have everybody on your Facebook Friends List because while SMS costs money, the messages sent through Facebook is free.

One of the key elements of Messenger is its notification system - even if the app is not open, if the user's contact fires off a message, the user will immediately get a push notification.

And if the user finds a contact annoying, the user can mute messages from the contact for an hour at a time (or entirely if he/she so wishes).

The Facebook Messenger app is currently available only in the U.S. and Canada and the mobile app that allows "real-time communication" will be available in other countries "shortly," according to Beluga co-founder Ben Davenport.

The launch of Facebook Messenger is significant because market research firm CCS Insights earlier this week said Facebook is now one of the top three providers of email messaging on mobile phones, according to a recent survey of mobile Internet usage in May 2011 across France, Germany, Italy, Netherlands, Spain, UK and the U.S.

According to CCS Insights, "Facebook is fast becoming the platform of choice for mobile phone users in Europe" and "is fast becoming the default destination for all things mobile," according to Paolo Pescatore, Director, Applications and Content, CCS Insight.

So, is Facebook Messenger a direct threat to Google+ Huddle or other group messaging apps like GroupMe and Fast Society?

It's too early to tell but it seems Facebook Messenger has the potential to become a threat to any group messaging app because if the user's friends and all his contacts are on Facebook, why would he/she care to use a non-Facebook messenger app now that the Facebook Messenger app is here?

Meanwhile, Google should watch out as the Facebook Messenger has two main advantages over Google+ Huddle:

> With Facebook Messenger, you can reach out to your phone contacts as well as Facebook contacts but with Google+ Huddle, you can only reach out to Google+ users.
> With Facebook Messenger, you can send text messages and photos and even let the person you're reaching out to, know your location. On the other hand, Huddle only allows you to send text messages.

What do you think? Does Google+ Huddle face a threat already? Leave your comments below.