I've always thought there could be an interesting use for Twitter just as a transport system for psuhing/pulling data between applications. You wouldn't follow those accounts, they'd just be data feeds. It's definitely not the use case Twitter started with, but it's viable now.

The advantage of using Twitter over another messaging system is that it's public and open. Anyone can easily push or pull from it without you having to build any additional infrastructure. On top of that it's reliable and can handle a lot of data.