There is something to be said about single-purpose Twitter accounts, bot or not. I have @earthquakesSF sent via text to my phone so I'm always aware of time and location of earthquakes. As for the New York Times, there is one account I think has unique value. It's @nytlive. They have defined a threshold of what breaking news is - and when it occurs, they send updates via this account. Helpful in emergency situations when power is down, like Hurricane Irene.