Double privacy fault
What annoys me about these kinds of programs is the contents of that address book. How does the Twitter Account holder become the one who decides if all those individuals on his address book agree to have their data stored on Twitter's servers to do with as the will?
My business email address is in many address books of my clients. And these idiot clients then upload MY personal data to the Twitter server without asking me first if this is okay.
And it is not just Twitter... I still keep getting invites from Facebook asking me to join, and then that shows me a list of other people I may know. And that list is often correct, and plain scary when I see the connections they have already worked out about me.
Of course... if you try and contact these companies to complain about use of my personal data that has been uploaded by a third party... there is no where to complain without a Facebook\Twitter\etc account. Last time I tried to chase Facebook to get my data removed, all their pages about it hit dead links