No wonder Facebook is so nervous. Twitter attracted 9.3 million unique visitors in March—a 131 percent increase from the previous month. This means that the site had more than five million new visitors passing through to see what all the hubbub is about. They didn't all necessarily open up accounts, though. An interesting side note: Twitterers tend to be news junkies, as they are two to three times more likely as average users to visit news sites. CNN alone has 939,000 followers on Twitter.