Facebook as well.. When I post one fan art in a FB group and a few people repost it and put "CTTO" (credits to the owner) which pisses me off that ain't crediting works. Also that repost got more attention to the original post which it pisses me off more.
I asked them to take it down and I get a bunch of people defending the reposter.. It was sooo.. tiring. Like they said, "if you don't want your art get stolen/repost, you shouldn't have post it on the internet
"
Oh dear glob, that logic is the same as "if you don't want to get murdered or get your stuffs stolen, you shouldn't have gone outside!"
This what made me to never draw fan art again on that popular series.... I still draw fan art but rarely now since I hate people for using my art.
I know this happens to other sites, but this is where I got it(for now) and it upset me so much.
Sorry for the vent but damn it still get me on my nerves.