Remember the tag was only put in place to help search engines in the first place. (Well, to stop people from spamming to get good search engine results. I think you get my point.)
So yes google can disregard nofollow on a case by case basis and face the associated potential legal consequences. I am sure that this would not be a problem in the case of stackoverflow, but I am not sure this is true in general.
As such, I don't think nofollow could have any possible legal consequences. It's intent is to indicate that you haven't vetted the links in question and as such are specifying a lack of trust in their content (i.e., user-submitted links); though like the article says, many people attempt to micromanage SEO through them which dilutes their usefulness (I've been told we have some links that do the same thing; no doubt someone thinking they were smarter than Google... so now we have to track them down and undo these pointless additions)
"You can browse my pages but you can't get useful information from them" is bizarre. I'm not saying that no site anywhere will ever sue over it, because this is America and you can sue over anything.
This is somewhat correct. While Google won't disregard noindex/nofollow directives (or robots.txt Disallow) it can - and will - show "blocked" pages in SERP if
the quarry is specific enough or a the page is "strong"
(lots of inbound links/strong social signals and etc...)
However, it will not show in page info (hide description and title) and use alternatives sources of information to fill those out instead.
For example: it can use DMoZ info instead of the real one.
I suppose it's selfish of me to want SO to share them and selfish of SO to mark them as nofollow and not allow the source articles to rise in ranking.
> StackOverflow is harming the quality of results in Google because they want people to filter through them for the information.
Well, no, actually. StackOverflow may be shooting itself in the foot. SO cannot dictate the rules of the search game to Google, and Google adjusts its SERPs pretty quickly, especially nowadays, when user behavior gets to have bigger influence on SERP with every ranking algo update. Poor quality content leads to higher bounce rate and lower avg. time on site and visit depth, which will inevitably lead to lower ranking and less traffic for SO. This (and perhaps a thousand of other factors) works for every site, and even more so for heavy traffic content projects like StackOverflow. So don't be afraid, the system will adjust itself.
Overall, I agree with your sentiment: I love SO, but nofollowing the Web looks kind of lame and selfish. After all, doesn't SO have its staff of moderators and admins to fight spammy comments?
Our suspicion is that when we clamped down on the spammers by banning accounts they reported our site for spam that they had created we lost 20% of our traffic - major brands like us can tough it out this could kill smaller sites without the runway to survive this or have "friends" inside the wire at Google.
I have had to help a small company completely rename and start again on a new domain after some one hacked the site and inserted 1000's of pages with links to porn sites.