I had the same problem with multiple account entry scammers on my own contest a while back which was extremely frustrating as I was forced to waste huge amounts of time investigating. I added a small rule that a ~0.01$ upvote is needed to enter which instantly removed all the scammers and the contest leechers that play just to cash out. Downside is that it's much less friendly and welcoming to new members with good intentions. With the SBD so high it's not that hard nowadays to quickly power up and it gives a good incentive for new members to 'unlock' being able to play along. Overall reaction has been very positive and some even powered up a bit and thanked me for initially kicking them from the contest. Also less work to manually run the contest and more of the prize pool is going to active members.