If you've been following my thread on why XMPP/Jabber is superior to all the other proprietary legacy protocols, then you should be beginning to see why Jabber is the king of instant messaging. Well, this reason takes the crown of why you should use Jabber.
First, I want to get the gears moving a bit in your head. Think about this for a second. When your send an email to you friend, can you only send him an email if he is using the same email provider as yourself? In other words, if you are using Gmail for all your email needs, can you only send an email to other Gmail users? Of course not! Don't be silly. You can send emails to people regardless of who their email provider is, whether it be Yahoo! mail, Hotmail, or some company email, and they can reply or forward as necessary to other people regardless of their provider. So, I have a question then: why do instant messaging providers make you keep rosters of only those who have the same provider? Why can MSN users only send messages to other MSN users? Why can Yahoo! users only send messages to other Yahoo! users? AIM? ICQ? See the problem? The reason being, only MSN users can connect to "official" MSN servers. Same with all the others. It's called vendor lock-in, and well, Jabber is different.
Not fair, is it? I have family that only have MSN accounts, thus, they only chat with other MSN people. This is troublesome, because I won't use proprietary IM protocols, so, as such, I can't chat with my own family unless they were to register Jabber accounts (which, actually, a few have). Yet, I can send an email to them just fine. See, email is completely decentralized, while instant messaging isn't. Jabber solves this problem by becoming completely decentralized just like email. Then, my family can have Jabber accounts with Gmail, while I run my own Jabber server at home, and I can chat with them with no issues. In fact, looking at my roster, the majority of contacts are using Gmail for their Jabber service, but there are also jabber.org accounts, a livejournal account, and a few in-house server accounts. Isn't this great? Regardless of Jabber provider, I can chat with anyone.
The magic behind this decentralization, is a service called "server-to-server". When I register an account, say at jabber.org, I can add anyone to my roster, regardless of their provider. What happens, is during the authentication, my provider (jabber.org) contacts their provider (say, gmail.com) asking for the contact's information. Their provider then notifies the user that an authentication is taking place. If the user approves, their provider contacts my provider saying all is well, and the user is then added to my roster. Think about this for a second. One server is talking with another server, even when out of domain. Would MSN do this? Yahoo!? AIM? ICQ? No way.
I know what you're thinking, for those of you who are proprietary IM users. Even though Jabber is decentralized, you can only send messages to other Jabber users, thus, still vendor locked-in to Jabber. You can't send a message to MSN or ICQ users- only other Jabber users. While this is true, this isn't Jabber's fault, rather, MSN and ICQ are keeping Jabber from communicating with their servers. Think of it this way: you have a Gmail account, and send an email to a Hotmail user. The email bounces, saying that you are not a user of Hotmail, thus, you cannot send email to other Hotmail users. You would need to register an account at Hotmail to send email to other Hotmail users. Look at how absolutely draconian that is! Email is completely decentralized, yet, Hotmail wants to lock their own users in. That is exactly the game being played in the field of IM. Jabber has solved the issue of vendor lock-in opening up the specification, and making IM completely decentralized, and yet, certain providers refuse to play along. So, for the time being, you can only send messages to other Jabber users, but I have a feeling, given the sheer number of Jabber accounts, that this won't last for long.
When I heard about the decentralization nature of Jabber, I was totally excited. To me, I thought, this would open up the IM playing field, and if providers didn't join in, they'll sink like the Titanic. Well, my thoughts haven't been too far off. Since the inception of Jabber, according to Wikipedia, Jabber is listed second in a raking of the number of users, trailing only behind AOL. About 90 million Jabber users are estimated. Given that article, this means that nearly a third of all IM accounts are Jabber accounts. I suspect that given time, more and more will switch to Jabber, as I have, and ditch their proprietary cousins. Wouldn't it be great, if there was completely and totally decentralized IM just as there is email? Hopefully, my XMPP articles will convince you that XMPP/Jabber is superior, and for you to register a Jabber account at a provider of your choice.