You may not have been happy to see this notice from Twitter pop up on your screen:
The control you have over what information Twitter shares with its business partners has changed. Specifically, your ability to control mobile app advertising measurements has been removed, but you can control whether to share some non-public data to improve Twitter’s marketing activities on other sites and apps. These changes, which help Twitter to continue operating as a free service, are reflected now in your settings.
Read more about the changes on Twitter.