From Twitter Status blog
In October 2006, just three months after Twitter launched publicly, we added IM support—i.e., the ability to get and send tweets via XMPP/Jabber/Google Talk. I was a big fan of this feature, because this interface, which millions of people were already familiar with, seemed a perfect fit for Twitter’s real-time nature.
In December of 2006, we extended that support to AIM, enabling a much bigger number of users to interface with Twitter via the same system they talk to their friends on all day.
While off to an early start, since then, our IM feature has been, well…spotty. We first killed AIM support after struggling for months to make it reliable (which was a side-project to trying to keep the service as a whole reliable). And our Jabber support has been up and down until about four-and-a-half months ago when it’s just been…down.
Oh yeah that's why I'm using Ping.FM alongside a range of other microblogging services such as Indenti.ca and Jaiku.