Mark Zuckerberg has taken to the stage (well, we say stage - the venue is basically a glorified canteen) to announce Facebook's new messaging service, previously called Project Titan.

And, despite the rumours, Zuckerberg was keen to point out that the new service isn't an email one. Except it is... a bit anyway. You will be able to have an email address (if you want one), but the over-riding idea is to collaborate all of your communications avenues into one conversation stream.

"You decide how you want to talk to your friends: via SMS, chat, email or Messages", reads a Facebook blog posting from Joel Seligstein.

"They will receive your message through whatever medium or device is convenient for them, and you can both have a conversation in real time. You shouldn't have to remember who prefers IM over email or worry about which technology to use. Simply choose their name and type a message".

Facebook is saying that the model is in fact more like chat. The aim is to provide a service that is "seamless, informal, immediate, personal, simple, minimal and short".

Zuckerberg's vision of a "modern messaging system" is aimed to tap into the 350 million Facebook users who send more than 4 billion messages (private and IM) a day, but his company is not targeting rival email services, at least not yet.

"This is not an email killer", the Facebook CEO said. "This is a messaging system that includes email".

"We don't expect people to shut down their existing systems, like Gmail. But, maybe one day people will say that this is the way it should be done".

It is designed to work with SMS, IM, email and Facebook messages. Facebook is saying it will integrate with other messaging services as well. IMAP support is on its way too.

There will be a "Social Inbox" that will let you personalise how you receive your messages.

"It seems wrong that an email message from your best friend gets sandwiched between a bill and a bank statement", said Seligstein. "It's not that those other messages aren't important, but one of them is more meaningful".

"With new Messages, your Inbox will only contain messages from your friends and their friends. All other messages will go into an Other folder where you can look at them separately".

The new service is going to be rolled out over the next few months, along with a new iPhone app that should also be showing up in the App Store soon. There are no details yet on when we might get it in the UK.

However, the initial wave will go out to invitees only, starting with those who attended Mark Zuckerberg's announcement at the Web 2.0 Summit.

What do you think? Will you switch your email account to Facebook? Let us know in the comments below...