One almost certain possibility: accounts for businesses, with tools to track who's saying what about one's employer. But with companies like Comcast and JetBlue already using the service for free, it's hard to see where the value lies. And given Twitter's simplicity, it's hard to see how advanced analytics are needed versus, say, just using the site's search engine.
Online publishers and ad agencies like Glam Media, Mashable, and Federated Media are making money by repackaging "tweets," or Twitter messages, and slapping advertising around them. Federated is voluntarily paying Twitter a cut from its Microsoft-sponsored ExecTweets site, but Glam and Mashable are just taking advertisers' money.
So what's Twitter doing about it? Watching, according to the Journal:
Fred Wilson, a Twitter investor and board member who is a partner at Union Square Ventures, says Twitter will make money by "following the money," or building on the ways that others are developing businesses based on the service.
In other words, as soon as someone figures out a good way to make money on Twitter, Twitter will kneecap them and steal their idea. Finally, a glimmer of business sense at the whimsical startup!