I can't say that i've ever really read anything on facebook by any of the "stars".... perhaps i've not been paying attention.
On here there are pages of info and route hints about just about every fell race ever ran. Not to mention advice on training/injuries/etc.... for the "rank and file" fellracer/runner i think this place has far more value.
I'll readily acknowledge that for keeping up with race dates/results/photos/changes of info, facebook is absolutely invaluable.