i don't have a facebook but i love instagram. i get to scroll through a feed of nothing but pictures of people's animals.
and yes, there are a lot of people in the hobby on instagram.
hashtagging is awesome if done right. for instance, if i search for the hashtag #retic or #reticulatedpython every picture someone used that hashtag in comes up. i've discovered a lot of people with awesome pictures of their snakes this way. it's just annoying the people that put "#" in front of everything just because they think it looks "cool"