HIVE is in itself anti spam because you first need RC/HP to post. That shuts out lots of the advert spam you were mentioning on Youtube in one of the comments.
Isn't the problem with spam accounts getting upvotes in itself negated by the community who will, presumably, NOT upvote low quality content? Or for that matter, the community is more than capable themselves of downvoting spam.
If the aim of HIVE is to grow into a 5million strong social network, then inane stuff which could possibly go viral like "youtube cat videos" are part and parcel of the ecosystem. Who is to judge whether that is spam or not? If everyone gets a laugh out of it, they upvote, or else they'll just move on.
That being said, "Who watches the Watchmen?"