ROFL - with all due respect to my dear friends, Pastor Thomas and Anhelyna, but their respective descriptions almost caused me to lose another keyboard to spluttered coffee.
I have used FB and have an account there still, but seldom use it lately - mainly because of time constraints engendered by my time here and working on the directory. My assessment of it, on the whole, would likely not differ much from what either of them have written, but I will admit that I do find it somewhat useful.
As one can tell from the timestamps on my posts, I keep odd hours - working late evenings and arriving home 'wired' post-midnight. Such makes it difficult to keep in touch with happenings involving friends and family who lead more 'normal' lives. So, in that respect, it is a help - though the incessant postings of near every jot of folks' daily living puts one in mind of 'reality' tv - which you couldn't pay me to watch (unless you paid me a very great deal, of course).
I struggled with the question of whether to include links to parish FB pages on directory entries, when those first became popular. Finally, I began adding them but with some trepidation because it isn't always clear which are 'official' (as in sanctioned by the priest) versus a parishioner's own well-intended but perhaps agenda-driven effort.
As many know, I am a long-standing advocate here of parishes utilizing whatever electronic means might be available both to educate and keep in touch with their current parishioners and to evangelize. And, like it or not, FB is medium by which one can do so.
As my brother and friend, Deacon Luke, notes of Holy Trinity's page, many are not highly utilized - but others I've seen are regularly flocked to by parish youth, viably promote church events, and - a few - seem to afford a place at which today's sometimes far-flung parishioners keep in touch with one another - something more easily done in a time when parishes were local and parishioners were your neighbors. I'm also aware of them being effectively used in lieu of a parish website by parishes that lack the finances, resources, or skills to create or maintain the latter.
So, I have to concede their value or potential value in those regards, though they are a nusciance from a directory standpoint, as it's much harder to find out who has one than it is to track down a traditional parish website. (LOL - how far we've come when I find myself speaking of parish websites as 'traditional'

.) As a result, there are many more out there than I have yet logged into directory listings and that will be the case for quite a while yet.
Many years,
Neil