Is there a way to see SQA statistics (e.g. number of visitors and number of active participants) over time? It would be interesting to see how the site is changing ( and how or whether it is growing).
That's an interesting question.
There are some analytics available to moderators, but unfortunately only generalities are allowed to be made public.
We're up in both visits and answers over last month, but down slightly in questions. Visits seem to be coming in heavily from search engines, which makes explains why more answers than questions.
So the growth area that is needed is definitely the questions. According to area51, a typical site will get 90% of its traffic from search engines, so we're on target there, which gives users their first question - the one they search. Our area of focus needs to be user's second question: the one they didn't come for but are interested in anyway. Those are what make them stay.