Rachael King, writing in Business Week, on how some companies use Twitter to boost their brands and to learn what's being said about them. An excerpt:
Begun in 2006, Twitter is a pioneer of microblogging, a way for users to keep others informed of their current status by way of text messaging, instant messaging, e-mail, or the Web. Other services that have followed suit include Jaiku, Pownce, FriendFeed, and Plurk. At this stage, many brands are sticking to Twitter, which has amassed a larger number of users. While Twitter doesn't release exact numbers, estimates range from 1 million to 3 million users.