The move came about six weeks after Twitter launched a trial of its own paid advertising service, called Promoted Tweets, which places advertisements at the top of search results. In announcing the ban, Twitter said it was trying to protect the "core experience" that has made the site successful, "with an eye toward long-term success for all advertisers, users, and the Twitter ecosystem."
"For this reason, aside from Promoted Tweets, we will not allow any third party to inject paid tweets into a timeline on any service that leverages the Twitter API (application programming interface)," Dick Costolo, chief operating officer at Twitter, said Monday in the company's blog. "We are updating our terms of service to articulate clearly what we mean by this statement, and we encourage you to read the updated API terms of service to be released shortly."
Costolo said some third-party advertisers are not "necessarily looking to preserve the unique user experience Twitter has created."
"They may optimize for either market share or short-term revenue at the expense of the long-term health of the Twitter platform," he said.
And, of course, there's the issue of money. Twitter bears the cost of maintaining the network, providing security against spam and other operating expenses, so it has the right to control advertising.
"The third party bears few of these costs by comparison," Costolo said.
For those advertisers affected by the ban, Twitter suggests waiting until the site launches a service called Annotations, which enables developers to connect metadata to a Tweet, making it possible for an outside computer system to attach extra content or links. Tweets are the messages users send on Twitter that have a 140-character maximum.
In the future, advertisers could try Promoted Tweets, a paid service currently being tried by a select group of advertising partners: Best Buy, Bravo, Red Bull, Sony Pictures, Starbucks, and Virgin America.
Twitter plans to eventually open Promoted Tweets to other advertisers and to Twitter partners, such as makers of Twitter clients. Later, the company plans to insert the ads in users' timelines "in a way that's useful to you," Twitter co-founder Biz Stone has said.