Twitter's new terms of service: Give us all rights to your words

This is the strangest bit of lexical legerdemain I've seen in a while.

According to the Sept 10 post on the Twitter Blog (which tries to explain Twitter's new Terms of Service in plain English):

Twitter is allowed to "use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute" your tweets because that's what we do. However, they are your tweets and they belong to you.

Pray tell me, in what possible sense does something belong to me if I've given every worthwhile right of usage over to somebody else?