Alan Rusbridger claims saying that Twitter has got nothing to do with the news business is about as misguided as you could be and explains why Twitter matters for media organisations:

1. It’s an amazing form of distribution
2. It’s where things happen first
3. As a search engine, it rivals Google
4. It’s a formidable aggregation tool
5. It’s a great reporting tool
6. It’s a fantastic form of marketing
7. It’s a series of common conversations. Or it can be
8. It’s more diverse
9. It changes the tone of writing
10. It’s a level playing field
11. It has different news values
12. It has a long attention span
13. It creates communities
14. It changes notions of authority
15. It is an agent of change

Well worth a read for how he explains each point in turn, and then concludes that:

Increasingly, social media will challenge conventional politics and, for instance, the laws relating to expression and speech. […] we can be sure that the motivating idea behind these forms of open media isn’t going away and that, if we are blind to their capabilities, we will be making a very serious mistake, both in terms of our journalism and the economics of our business.