Now that there are number of area51 sites in public beta, I was wondering what metrics were being considered to determine which (if any) of the sites would make it to non-beta stage. I understand that the beta period is 90 days, so the metrics might not be laid out yet, so this is more of a 'what are the SE overlords thinking' kind of question.
The thinking is don't publish some kind of crazy, convoluted "You must be THIS tall to ride" equation until you have sites and data to test it on. You can see from our current crop of sites that we haven't hit that "Oy! This has got to go, ASAP" scenario. So, anything we come up with today will probably make no sense a few weeks from now.
When you see that a site doesn't work, you look at it and ask "why?" "Can it be fixed or does it need to end?" "What other fail scenarios do we have to consider?" Then you look at whatever criteria you feel where that site falls short and set the bar just above that point.
Sites will vary widely in size and purpose. Two posts per day on a "Mesothelioma Treatment" site might be a block buster for that community. Two posts per day on a video game site would be an epic fail.
Not only is there very little experience in what makes a SE-type site successful, quantitative critera can be gamed. In the pre-commitment phase, there's a temptation to only vote questions on- or off-topic if they seem likely to hit 20 net votes. I don't think that's a big problem, but going from public beta to permanent is one of the most important decisions, and really shouldn't be easily gamable.