Nature gets seen side by side with free access journals there, and so now we get to see them for free (regardless of delivery mechanism). It likely doesn't matter what Hacker News thinks about this. Our impression of free, say github style open source free is otherworldly different than Nature's free: paywall, peer reviewed, exclusive, ultra prestige. Tomorrow there will be celebrations in my old lab about how amazing this is.
[1] http://sci-hub.org/ [2] http://booksc.org/ [3] http://www.freefullpdf.com/
I have actually tried to do what you are suggesting before, so I could bulk-download PDFs (I have an institutional subscription). The problem is that the URLs are different for every journal, and some have Javascript that makes automated downloading hard. Since there are thousands of journals, it's very tedious to try to invent a generalized solution.
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.