<i>We had AIM, Yahoo, and MSM. We learned that is stupid as hell, and we should just use the same protocol. So then they all supported XMPP.</i><p>I think you are misinformed.<p>AIM: Never supported XMPP<p>Yahoo: Never supported XMPP<p>MSN: Never supported XMPP<p>What happened was that someone wrote code to send messages between them all. However, you still needed accounts on each for it to work.<p>Source:<p><i>No service can talk to all services. This means in order to talk to contact X, you must have an account on the same service as contact X, or on any compatible service.<p><pre><code>  If you have an account on AIM, ICQ, or MobileMe, you can chat with anybody who uses AIM, ICQ, MobileMe, or SMS.


  If you have an account on XMPP (&quot;Jabber&quot;), Google Talk or LiveJournal, you can chat with anybody who uses XMPP (&quot;Jabber&quot;), Google Talk or LiveJournal.

  In the official clients, MSN users can chat with Yahoo! users but this is not yet supported by Adium.


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Some XMPP (&quot;Jabber&quot;) servers (mostly private ones) allow chats with proprietary services such as AIM, MSN, and Yahoo! via a mechanism called &quot;XMPP transports&quot;.</i><p><a href="https:&#x2F;&#x2F;adium.im&#x2F;help&#x2F;pgs&#x2F;Accounts-ListOfServices.html" rel="nofollow">https:&#x2F;&#x2F;adium.im&#x2F;help&#x2F;pgs&#x2F;Accounts-ListOfServices.html</a>