They are trying to put specific questions to specific stackexchange subsites. So, there is http://programmers.stackexchange.com for conceptual questions , http://cs.stackexchange.com/ for "easy" computer science and http://cstheory.stackexchange.com/ for "hard" computer science.
I don't see the problem in trying to split the horde of questions into more subsites.
First, the idea that questions can be easily classified into discrete categories is bullshit. Why have they set it up so that multiple tags can be assigned to individual questions? Because most, if not all questions span genres. Not only is it possible for a submitter not to know what category a question goes in, but it is also possible for the same question to legitimately belong in multiple categories.
Most importantly, however, the populations asking and answering these questions (or that you want asking and answering these questions) are not different. Do you really think that people answering questions under "programmers" and under "cstheory" wouldn't also be suitably answering questions under "cs"? Would a question posted under "cstheory" not be useful to people posting under "cs"? At what point in one's academic path does one transition from asking questions in "cs" to doing so in "cstheory"? After your second year of college, after graduating, or after being accepted to a phd program?
Think about it mathematically. Take 1,000 people posting in stackoverflow, divide that population in half and distribute one half of them equally between programmers, cs, and cstheory. The total possible connections and interactions between people in communities of size 500, 167, 167 and 166 is far fewer than the total possible connections and interactions within a single community of size 1000.
I had actually not heard of there being different stackexchange sites for "programmers", "cs" and "cstheory" before reading your comment. What a ridiculous thing to do, to split up these sites. And then to shut down popular questions inside stackoverflow in order to push people into these marginal sites? Talk about shooting yourself in the foot.
I'd argue that Snowboarders have a very different culture than Skiiers, with their own sets of terminology, equipment choices, and social norms. That's why they need a community to themselves, with their own moderators, reputation systems, and ideas of what kinds of questions they find on or off topic.
That's how they want it. Stack overflow is not about being "interesting", it's about being relevant to common problems.
So I'm left with a choice. I can not see those questions. I can answer those questions on a site where I know that is not wanted. I can become one of the people trying to moderate the site into the structure they want despite knowing how frustrating that can be for the people affected. None of those options is palatable to me, so I'll find other ways to amuse myself.
Look through my answers at http://stackoverflow.com/users/585411/btilly?tab=answers and tell me whether the loss of contributers like me is good or bad to the whole stack exchange enterprise. If you think it is neutral to good, then our value systems are so different that there is no real point in continuing the conversation.
I actually agree with the demarcation between sites for some of these concepts, as it gives opinion and other background concepts a place to flourish (cf, programmers stack exchange).
But this tendency to want to create a perfect little taxonomy and then track down every bit that defies your view of that taxonomy is an unfortunate side effect, IMO. It happens far too frequently that good questions get knocked down that hole inappropriately, and it's never a good experience for the users when it does.
I'm honestly surprised that the site has never found a better way to deal with the problem. When most users who encounter a problem like this for the first time feel insult at the site's action, perhaps there could be a gentler way of redirecting their energy?
A Venn diagram including stackoverflow, programmers, ux, dba, cs, cstheory, security, codereview, and a few others, has substantial areas of intersection. There are over 37,000 stackoverflow questions tagged "database"; surely an exhaustive search for answers to some database-related questions would include both stackoverflow and dba. (Do answers from smaller SE subsites appear lower in Google search results?)
What if SE explicitly worked with a graph whose nodes are all the SE sites, their tags, their questions, and their answers? When seeking answers to questions, we don't care which site we find them on, so why not turn the SE browsing experience into one that can cross site boundaries? As far as I can tell, currently the only explicit edges among such inter-site nodes are the "this question migrated from site x" notices. The danger of the dilution of the SE network into something like Quora would be mitigated by the fact that there would be very few edges connecting bits of sites like stackoverflow and diy.
Surely there's value in seeing how data at the various sites are interrelated, mining those Venn diagram overlaps.
Tangentially, it's evident from the gripes here and elsewhere that there is substantial value in many of the "closed" questions. Instead of closing questions, perhaps they could be routed to some sort of alternate track, usenet alt-hierarchy-style. These questions would still be participants in the overall SE graph; let the user make an affirmative decision to opt in to the "alt" portion of the graph as part of their registered-user SE experience.
Prior awareness of how one's question would be categorized with respect to all the relevant stackexchange subsites falls into the realm of "don't make me think".
Beyond that, if there are a lot of "just barely" off-topic questions being asked, that is a good reason to launch another sub-site; this is how Super User (power computer users, any OS) and Server Fault (sysadmin) sites were launched, because there were a ton of these sorts of questions being asked in the early days of Stack Overflow, but they weren't really about programming.
We've also seen some subsections of the Stack Overflow community want their own sub-site, because they legitimately form a unique, strong community of their own: like DBA (database admins) and Mathematica. All those questions are technically on-topic for SO, but the community wants their own place, with their own reputation system, their own moderators, and their own take on what questions they'll allow.
"The danger of the dilution of the SE network into something like Quora"
This made me laugh, but Quora's problem is that they allow and even solicit pure opinion, whereas on Stack Exchange we prefer answers that can be verified in some tiny way. "Because that's what I think" is a valid reason to answer anything on Quora, which gets into unpleasant weirdnesses like judging answers based on the fame/success of the answerer, because, well, what other science can you apply to an opinion?
As someone who's had a few questions shunted from SE site to SE site, being closed at every step, I think SE would do well to emphasize migration over closure. Having a question closed is a real downer, the opposite of all the SE game mechanics. And it's one of the oldest principles of UX: Don't tell me what I should have done. Just do it for me.
And some of the "subjective" questions produce fascinating discussions and enlightening answers; arguably the community moderation of such questions and answers (closing and deletion notwithstanding) still provides valuable weighting that could influence the overall graph and increase the value of the network. Could there be a shadow network still moderated for quality? Hard problems but fun to consider.
That is, you gotta do your homework, and not everyone can get into Harvard. Or even their local community college for that matter.
But I'd say the proof is in the pudding, that is, look at what percentage of pages SE generates that are actually useful and make the Internet better.
Clearly the question and answer was useful to someone, code related, interesting to others (upvotes), so excluding it only serves to discourage great contributors, with the proposed solution being division of the audience.
Programmers I can understand, as it seems to be more about the art of programming as a practice. (e.g. software engineering)