How does Steemit deal with fraud and spam?
steemit.com is a self regulating social network, it is up to the users to regulate it how they see fit. It is definitely not the prefect system because even though it is much more democratic than any other social network it is not completely democratic because the users who have the most invested in the STEEM blockchain have more voting power.
Problems can arise because when a user downvotes content, the user who he/she downvoted can downvote their content simply as retaliation. And the user who has more STEEM power will always win. So it forces people to be kinder to each other because they will lose reputation points and money, but of course there will always be some people who will try to take advantage of the system.