Proof of Brain means Proof of Brain. That's the beauty of the Steemit system. It essentially means you have to add something new and original. Even if you are citing other material, there should be something original and new brought to the community and that's what we see with the people upvoted above. I was grateful to be recognized by curie last week and I've seen curie be very active in the #steem-cartoon and #comics community. It's like pouring rocket fuel into the creative community.