The data itself still appears to be relatively innocuous. Twitter has described it as a randomized sample of public tweets covering the period between December 2014 and April 2015. It shouldn't compromise any direct messages, then, and users with private accounts also shouldn't be affected. Even so, it's understandable why Twitter users might be concerned. GSR harvested and passed along the Facebook data from tens of millions of users without their consent, and there's a real concern that it might have tried the same approach with Twitter.

Update 4/30/18 3:57PM ET: Despite Cambridge Analytica's statements in its defense, Twitter has now blocked the company from buying ads on the social network. Recode reports Twitter cites Cambridge Analytica having a "business model that inherently conflicts with acceptable Twitter Ads business practices" as the reason for the action.