Twitter changes service terms to 'leave door open' to ads

Twitter Inc., the short-messaging social network, made changes to its terms of service that may allow advertising on the Web site as it searches for ways to generate revenue.

"We leave the door open for advertising," the company, whose service is free to users, said yesterday on its blog. "We'd like to keep our options open, as we've said before."

Twitter is seeking ways to spur sales without alienating users, after reaching 20.1 million U.S. subscribers in June, according to researcher ComScore Inc. Earlier this year, larger rival Facebook Inc. backed down from some modifications in its service terms after users complained the site had too much control over their postings.

According to Twitter's new terms, the San Francisco-based company and its partners may place advertising on the site, in connection with content submitted by the users.

Twitter is also exploring rules for applications that have grown up around the service, the company said in a draft of developer rules on its site. Developers have to get users' permission before sending messages on their behalf or creating a product featuring users' postings, like a t-shirt or poster.

Twitter, the third most popular U.S. social network after Facebook and News Corp.'s MySpace, is also considering adding paid services for corporate users, such as a tool to help businesses monitor postings, or 'Tweets,' that mention them, co- founder Biz Stone said this week.