Somewhere in the past few hours, the millionth question was asked on Math.SE. Could someone cleverer than I am please figure out which one it was. Presumably there should be a plaque or statue, or somesuch commemoration. What would be suitable recognition for the questioner and the answer(s), if any? It will be interesting to see if it's a "good" question.
Any reasonable definition of "millionth question" would have been fine with me. But, to placate the folks who feel that this question is "opinion-based", let me suggest a definition: the millionth question is the one that caused the counter at the top of the main question page to reach 1,000,000 for the first time. By this definition, it was apparently Firat Celebi's "Separation Properties in Topology" question.
I have always felt that inventing suitable definitions is an important part of mathematics. It surprises me that so many people are critical of any question that requires such an invention.