Bookmarking this as we're really glad there is discussion about it. Even though we haven't seen any abuse as of yet we'd like to make sure any issues are addressed before they arise i guess. It may all end up hypothetical or minimal but it's still worth looking into.
The first comparizon that comes to mind is Voting on comments is also a medium for abuse where people can write dozens of comments and upvote their own comments... but the good has outweighed the bad, even though users can hid votes inside of thousands of comments.
I guess voting at all is a system that allows the ability of abuse.
Anyway I'll go back through it and maybe collect some more thoughts more closely related to what was written in the post. Thanks for spearheading the conversation.
I am really glad that this feature has finally arrived and I think with experimentation, it could be great for Steem :)