Twitter received 4,410 DMCA takedown notices last year alone. But while previously a successful claim would lead to a tweet being vanished under dark of night, from here on out it will be replaced by a notice that it's being withheld.
The tweet in question will still be gone and irretrievable, so this won't lead to a DMCA revolution. But it's nice that there's a permanent record now of the time you were smote by the copyright zealots. Wear it as a badge of honor. Or at least, one of transparency. [GigaOm]