Did you read past the first paragraph? They mention some recent changes they've made:

To respond to that challenge, we recently launched a redesigned document-level classifier that makes it harder for spammy on-page content to rank highly. ... We’ve also radically improved our ability to detect hacked sites, which were a major source of spam in 2010. And we’re evaluating multiple changes that should help drive spam levels even lower, including one change that primarily affects sites that copy others’ content and sites with low levels of original content.

And they are saying pretty clearly they think they can do a better job on content-farms:

Nonetheless, we hear the feedback from the web loud and clear: people are asking for even stronger action on content farms and sites that consist primarily of spammy or low-quality content. ... The fact is that we’re not perfect, and combined with users’ skyrocketing expectations of Google, these imperfections get magnified in perception. However, we can and should do better.

To respond to that challenge, we recently launched a redesigned document-level classifier that makes it harder for spammy on-page content to rank highly

When is recently?

We’ve also radically improved our ability to detect hacked sites

Since when; all the complaints I have read are from the last few weeks, and when I looked up a medical complaint this week?

And we’re evaluating multiple changes that should help drive spam levels even lower

Oh, are you now? Of course... Translation 'We are looking into it'. D'uh.

that copy others’ content and sites with low levels of original content

This last part is the only datum I got from the article - they explicitly respond to stack overflow, etc... It is still fluff though.

What I would have preferred: I made a change on 2011-01-15 and you should see it here, here, and here. 'Here' can be broadly defined.