Twitter: Rate limits are to eleminate bots

Twitter says recent rate limits on Twitter are implemented to detect and eleminate bots and only a small percentage of users are affected:

To ensure the authenticity of our user base we must take extreme measures to remove spam and bots from our platform. Any advance notice on these actions would have allowed bad actors to alter their behavior to evade detection.

The company says these actions intend to prevent data scraping from users and state that the restrictions are temporary:

Currently, the restrictions affect a small percentage of people using the platform, and we will provide an update when the work is complete. As it relates to our customers, effects on advertising have been minimal.