This question already has an answer here:
So it's crossed my mind recently in relation to a few of my questions that they would be quite appropriate on more than one Stack Exchange (Area 51) sites. My question is, is it considered acceptable/appropriate to post an identical question on, say, two different SE sites?
To give a concrete example, I recently asked the question entitled The Power of Lambda Calculi on math.stackexchange (Mathematics), but soon thereafter it would be almost as appropriate on cstheory.stackexchange.com (Theoretical Computer Science).
Any thoughts on this general issue (or even specific case)? Should users be permitted (or even encouraged) to cross-post in certain rare cases where the subject matter is germane to more than a single SE site?