I thought the all QA here should be covered by mathoverflow.net?
I am personally torn about this. It is great to see top mathematicians and computer scientists interacting about deep questions. I also participate in both MO and TheoryOverflow (or whatever we decide to call ourselves).
However, my strong impression is that the TCS community at MathOverflow is a small and marginal part of the site. Only the most clearly mathematical questions appear suitable for MO. If there isn't a direct relationship to set theory, foundations, or logic, or the question isn't related to a hot complexity topic to which heavy mathematics machinery has been applied to, then the question and its answers appear likely to remain in a dusty corner of the site.
Of course we could encourage the TCS community to join MO. But I think there is a strong part of the TCS community (at least as defined by EATCS, if not SIGACT) which is altogether unlikely to find its questions relevant to MO. I would like to see questions about
and I don't think any of these questions would currently be welcome on MO.
I'm interested in almost every question posted here, but I am interested in only a tiny smattering of questions on MO. To me it's simple. TCS and math are two disciplines that speak the same language, but have different overarching concerns. In fact, a better comparison for me is TCS vs theoretical physics, in that both disciplines use the language of math to study phenomena that have a specific nature.
Since we haven't absorbed all theoryCS folks into math departments, I see no reason why the same should happen here. Since there's a lot of cross talk between the disciplines, the same will happen here, and I don't see that as a problem.