One of the things that has impressed me about Twitter is the speed with which developers have adopted the API. There are more than 20 desktop applications and more than a dozen mashups listed on the Twitter Fan Wiki. The Wiki also lists non-humans that you can follow.
The CNN bot (and probably some of the others) was created by someone not associated with network. That’s one of the great things about open data and open APIs — motivated users can create new products. It’s unlikely that anyone at CNN or Twitter would have done it so quickly. I could see Twitter being used for Amber alerts or emergency weather updates.
Because Twitter can send messages to cellphones and IM, it’s an easy way to add alert capabilities to existing sites. That’s only likely to increase with the release of new APIs that allow more direct access by publishers.