I was wondering why there is not one single Stackoverflow for all type of questions (where we have the different portals now, like meta.stackoverflow, the basic stackoverflow, superuser, math.stackoverflow, etc). There could be some basic tags like programming or meta or math or so.
It would make the moving from one site to another (or just closing because it fits nowhere) obsolete. It would be just a retagging. Thus is would simplify the process when posting on a wrong platform and avoid confusion for newcomers. In many cases, a visitor of stackoverflow.com sees that there are many computer related questions and will post his own computer related question there.
You would also share your same account for all sites. (This would solve automatically the problem described here. For a possible solution about the reputation, see below.)
I often felt the need to ask some non-programming question but was always to lazy to figure out what other sites there are and where my question would fitt best. And also the need to create a new user account annoyed me.
In case it is wanted to have different reputation for each major topics, that can be done technically (like assigning tags to each reputation point - or at least seperate them by the major topic).
In case someone really only want to see only questions of a certain kind, there can be some filtering. And also all domains like x.stackoverflow.com could automatically filter for the major topic tag x.
To not allow any random question, you could force the use of at least one major topic tag. And any question which are unwanted on Stackoverflow could just be closed. (To maintain some quality.)
Edit: I just figured out that math overflow is not related at all to stackoverflow. This adds of course some non-technical difficulty to the issue. And esp this would have been a good example to my proposal as I can see a huge intersection of computer science and math. (Whereby I am not sure if stackoverflow is just about technical questions or also about computer science in general.)