I think you will find some of our members spend a LOT of time of Facebook, whereas they used to spend a LOT of time with us.
Well, bk, if you happen to notice that "some of our members spend a LOT of time on[sic] Facebook", then that must mean that you spend a lot of time "of" Facebook too. Right? Well...

If you're keeping track of people on Facebook, then, well...

Also, with Facebook's ever-changing format and notification system, it can look like some people are more active than they actually are especially if they have activated notifications for some of the "daily" applications like Horoscopes, Quote of the Day, some of the charity apps, etc. You may see "activity", but that doesn't mean that they are active.
Have you considered asking your Muse, Margaret, to post? Or would that be sort of like a conflict of interest? Or just something that is best the way it is?