[2016]: I have the subjective impression that the rate at which interesting questions and answers are being posted on cstheory.stackexchange.com has decreased substantially over the last year or so. Does anybody else have this impression (maybe answer that in a comment)? Or even better, does anyone have access to cstheory.stackexchange.com metadata to check this trend objectively?
[August 2018]: Moved the data that had accumulated here down into a community-wiki answer, and posted updated data suggesting that, as of 2018, the downward trend seems to be continuing (see chart at end of post).