Lee Munson, Security Researcher at Comparitech.com:
Given the fact that the service has strict rules on how personal data may be used and shared by third parties, especially in terms of prohibiting advertisers from targeting anyone based on sensitive information, such as gender, sexual orientation, race or religion, the typical user has nothing to be concerned about.
Also, with the ability to control what is shared via Twitter’s own privacy settings, users are afforded a great deal of control over what they share and who can view that, as well as how they can be found and identified on the service.
The only privacy concern I have in regard to Twitter is the level of personal and sensitive information people willingly share themselves via their own tweets.
Raising the retention period for user data from 10 days to 30 will not affect any of the above in any way.”