After having already alienated some developers with its Twitter apps for iPhone, Android and BlackBerry handsets, popular micro-blogging site Twitter said in a May 24 announcement that it is revising its developers' terms of service to ban the insertion of paid ads into the Twitter stream by third-party advertisers.

The move, which essentially aims at protecting the site's embryonic `Promoted Tweets' ad business, implies that third-party advertisers will not be able to inject paid tweets on any service leveraging the Twitter API. In addition, third-party advertisers will have to pay Twitter whenever their content is leveraged in an ad sale.

Furthermore, forbidding third-party ads on Twitter site will also help the company control the monetization and integrity of its service; and ensure a firewall for blocking out ads that taint Twitter's coherent "timeline."

Noting that the move will also preserve Twitter's distinctive user experience, Twitter COO Dick Costolo said in a recent blog post: "As our primary concern is the long-term health and value of the network, we have and will continue to forgo near-term revenue opportunities in the service of carefully metering the impact of Promoted Tweets on the user experience."

In an interview with All Things Digital, Costolo also specified that the move will not affect those services which do not generate revenue, and those whose revenue comes of subscriptions and other advertising-unrelated products.