I'd like to compare users according to how frequently they view the site. On Stack Overflow, is it possible to view a list of users, sorted by their likelihood of being online (so that I can tell whether or not they are likely to respond to other users' posts)? (It would be possible, at least in theory, to determine the likelihood of a user being online. This could be determined by the number of times that a user had accessed the site in the last day, month, week, or year).
If I wanted to respond to one of the users who had closed a question (to determine exactly why the question had been closed), I would want to respond to the user who was online most often. However, there's currently no way to compare the activity level of multiple users at-a-glance.
Also, there's a related question that discusses the possibility of determining whether or not a user is currently online.