Stack Overflow receives about 15,000 new questions a day - not counting those that are deleted within a few minutes of being posted.
As described in this post there are really too many for experts to get a good look at, a lot of bad questions aren't receiving the right type of exposure to janitorial effort, and a lot of good questions aren't receiving the right type of exposure to expertise.
Past efforts to resolve the problem
When this problem first reared its head the fix was to customize the home page (hot questions) and show questions the user had a likelihood of understanding and answering, based on previous site activity, in addition to those the user marked as interesting.
When questions started falling off the front page before finding an answer, we got the community user to 'bump' unanswered questions occasionally in the hopes that someone who could and would answer would come along and happen to see it for the brief time it remained on the home page.
Next step: splitting?
I believe we've outstripped ourselves.
Is there any merit to the idea that splitting the site up in some way to cater to different programming communities or to different programming experts would alleviate this problem?
Specific implementations aren't the point of this discussion
There are a million ways we could "split" Stack Overflow, and the discussion(s) surrounding that would be exceptional in length and thoughtfulness. Endless discussions on what loosely established communities exist in the programming world, and endless discussions on how to effect the split, whether simple (aggressive filtering of the hot page to only topics a user has successfully answered in the past) to moderately complex (subdomains with aggressively filtered tags, a subdomain for each language, or community, etc), to actually creating a new area51 proposal for each community, forcing them through the process, and building real "new" sites. This doesn't even approach the questions surrounding reputation issues and so forth.
It is a very interesting set of questions that we could spend days and weeks yammering on about, but How Should It Be AccomplishedTM is a different issue from this discussion, so please try to limit answers and comments to what positive effects can be gained from a split of some sort, and what negative effects might be experienced due to a split.
Is a split worthwhile?
Keep in mind, however, that I'm using the term "split" very loosely. It might be a UI tweak, or it might be parting the Red Sea, and never the twain shall meet between the resulting sites. I don't know. If your thoughts on positive and negative effects depend on the type of split, assume the split that you believe provides the most positive and fewest negative effects, and describe it very briefly (two sentences at most...) so readers are on the same page as you.
However, if you can, try to discuss this at a higher level where the implementation shouldn't matter. It wouldn't be a complete fix, or resolve the situation completely, but would it be helpful?
There are over five million questions on Stack Overflow. Of those, 10% have 0 answers. That's after excluding closed, migrated, or duplicate questions.
Of those that have answers, only 51% have more than one answer.
I believe the premise, that Stack Overflow is overburdened and isn't doing as well as it could be at answering questions, isn't false.
If it is working as well as it should be, and these 500,000 unanswered questions are outliers, then nothing needs to be done.
If it isn't working as well as it could be, could splitting it be a solution, or not?