updated 04:50 pm EST, Tue February 28, 2012
Phones previously a safe haven
Twitter is now allowing promoted tweets to appear in the feeds of iOS and Android apps, according to an announcement. While promoted tweets are nothing new, these have so far only been displayed via the twitter.com web client. Advertisers will initially be limited to displaying tweets to people who already follow them on Twitter, but in coming months that restriction will disappear. For now, iPads will remain without the extra ads.
The expansion may upset some Twitter users, since smartphones have been essential to the service's popularity, and have so far been a safe haven. The company's mobile clients do have some advertising, but only in a style similar to other smartphone apps. Promoted tweets appear mixed in with the content a person chooses to receive, adding clutter.
Twitter is thought to be making the move to increase its ad inventory. The company recently started a self-serve advertising program, and likely expects an influx of new ad buyers. Any new ad buys will include mobile by default.