People will always try to game the system, but the harder it is to do so the better. It's not impossible to have many facebook accounts and link them. Time consuming yes but not impossible. But it doesn't really matter until an investment is made since steem power can't be transferred. You can't make 100 accounts and move all the steem power to one account. And people who find plagiarism should recieve rewards, and repeat offender who do not source/give credit to the original creator, should have their accounts suspended. I think it's a matter of tableing all ideas and seeing what works best to implement as many good ideas as possible.