The one possible privacy problem that I can see is that they are selling tweets that users can no longer control - if I said something a year ago that I wish I

The one possible privacy problem that I can see is that they are selling tweets that users can no longer control - if I said something a year ago that I wish I could take back ("Hi everyone, just to let you know I'm gay" or whatever), I'm now unable to delete it, or even review what it was I said, but it can still be sold and tied to me. Still, not something I personally have an issue with, and I suspect not something most people would have an issue with.