Former Facebook intern. The number they track is number of accounts with activity in the past 30 days. Logging in to Facebook or performing some other action associated with your account is sufficient to trigger this.
When you say "performing some other action associated with your account" does that mean:
1) you can perform actions associated with your account without having been logged in? If so, could you give an example.
2) someone else can perform an action, and that would mean you would be considered active even if you hadn't logged into Facebook in over 6 months. If so, could you give an example?
I interpreted 'logging in or performing some other action' as 'we do not want to count users as active when they stop using Facebook without logging out'
So ... I ask not being a FB user myself: if I have some kind of facebook "toolbar" (I assume there is one?) installed in my browser, and it's configured to automatically log in, then I am an "active" user even though I may not be interacting with FB in any other way?