The public link is probably coded to each subscriber, so they would be able to identify the culprit and disable all the links from that subscriber.
I expect all Nature articles made "free" today to be available on TPB in one month. I'll put .1 BTC on it. :)
But regardless of what DRM scheme they choose, it's doomed to fail, all it takes is one person to crack the scheme and liberate the underlying documents. Alternatively, since 100 anointed blogs and media outlets will apparently have the right to download raw PDFs, all it takes is for one of their accounts to get hacked.