Why can't we all just get along?
Can anyone tell me why there is no widely adopted protocol for instant Messaging software? Every web browser and web server use HTTP. Want to transfer files with your favorite FTP client? No problem, they all use the same protocol. What about sending and receiving E-mails? There's always POP3 and SMTP. Telnet and SSH are the same story. Sure, there's some different flavors, but most all clients are interchangeable. Why then, must I sign up for AIM, Yahoo, Skype, ICQ, and MSN just to keep in touch with everybody? Trillian sure helps, but I still have to have all those accounts. Why? Why can't we all just get along?

At least on the client side we have Trillian which works with all networks.
Each network has its own strengths too. Skype is best for video quality and GTalk is best for audio quality. MSN has poor latency and network reliability even when just typing.
Even if all the instant messaging services suddenly adopted a uniform protocol, you'd still need your login to use each of their services.
I suppose what the services really need is an intra-service gateway, so MSN Messenger users can reach Skype users, etc; that way one would only need a login for the one messaging service of choice, and one could communicate with people on different messaging services. Again, this is not a protocol issue, as it's immaterial what the protocol from client to server, and between servers is, provided the gateways translate it. I agree it would be _easier_ if there was a common protocol.
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Adam
http://www.xmpp.org/
it does have issues (which Adam alluded to): incompatable services, usually by Microsoft (webcam, file transfer, etc)
another is that it keeps the sysadmins on their toes. they might have blocked MSN at work but there's three other services to try and knobble.
meh, my 2c