Ignore Twitter? Major brands learn they'd better respond -- and quick

Amazon.com Inc. shut like a book. Domino's Pizza Inc. was late but eventually delivered. And CNN focused on the good news.

When the three major brands engaged with their Web-savvy fans and critics in separate incidents last week, their responses demonstrated how corporations are still learning how to control their messages -- and reputations -- in a fast-twitch online world.

The mixed track record so far shows that fluency in the evolving language of digital public relations comes easier to some companies than others.