That's an interesting move. The DMCA offers a wonderful save haven for companies who allow users to post content, but that safe haven is eliminated upon refusal to act on a takedown notice like this. The article says, "It's not clear Facebook is fully aware of what they’re stepping into". I'm shocked that they would risk being found liable for these user actions because they didn't act on the takedown notice. For a company struggling to find funding, now is not the time to make a stand that could bankrupt them.
/This is not a commentary supporting the DMCA or US copyright law, merely a commentary on the legal risk Facebook might be contending with here.