Off of Techdirt.

Yahoo Blocking Trillian Again -- This Time They Say They're Serious

In the ongoing battle to keep their markets smaller, rather than as large as they can possibly be, the various instant messaging platforms still refuse to come up with a single standard to communicate across systems. Every time I complain about this issue, someone says "just use Trillian." That would be a great solution if the various IM providers didn't keep blocking Trillian. Yahoo has now announced that, not only are they now blocking Trillian, they're going to continuously change their protocol to keep blocking Trillian. Of course, it was just a few months ago that they claimed the exact same thing, and just like with Microsoft, Trillian quickly patched through the block. However, the difference this time is that Yahoo is bringing up the dreaded "spam" excuse for why they're serious this time about the block. They claim they need to do so to keep out IM spammers, but it's also a convenient excuse to block out a third-party IM client on the misguided belief that a walled garden somehow helps them out, rather than taking away the network effects of an open, interoperable system.

Source: http://techdirt.com/articles/20040623/2314236.shtml

Being an avid fan of Trillian I have been a victim of this. Every few months or other, Trillian stops connecting to Yahoo. Now the interesting point is that Yahoo Messenger users never seem to notice. Now that sparkles interest doesn’t it. The fact that the Yahoo Messenger client is able to dynamically adapt to change its protocol. My current suspicions border around the idea that its not a complete protocol change, but only a change to the security handshake.