Twitter's web interface has long been populated by innocent-looking tweets, trends, and accounts that pop up because they've been "promoted." Twitter's mobile clients have been mostly free of these ads to date, but that's about to change: the company has announced today that promoted tweets and accounts will soon make themselves at home in your timeline and searches, respectively, when you're using the official Twitter client for iPhone or Android.
Twitter says that the changes will make their way onto your phone in the coming weeks, though some people that already follow promoted accounts might see promoted tweets in their timeline before then. Like in the web interface, Twitter promises that you'll be able to dismiss promoted tweets when they aren't helpful, and the company says it'll collect that data to provide ads that better suit you. However, unlike the web client, promoted tweets won't always show up at the top of your timeline — they'll be tossed into your stream at a yet-to-be-determined point. If you want to avoid the ads, you can just switch to a different client — third-party Twitter apps don't have any ads yet.