That's not right mate. Had a lot of that recently it's getting ridiculous simply limiting the amount of accounts from the same I.P would help fight this. I highly doubt its a group of synchronized trolls it is more than likely individuals with lot's of accounts.
They are getting more and more obvious. Really good memes disappearing from the front page with 800 views and 94 upvotes when other peoples are on for 15,000 views and 164 upvotes. It's being done in attacks with multiple accounts to either stall a meme, send it back to submitted or remove a threatening meme from sight with a sequence of downvotes. Once the meme has a sequence of downvotes it's ratio compared to other up and coming memes doesn't compare so it drops effectively out of sight.
I've been closely watching a few users.