One site that does this is streemian, which is down.

What do you mean streemian is down? I'm following steemSTEM's trail with it and it's working fine. Or do you mean it occasionally goes down?

The general question is nuanced. If everyone had a substantial upvote, like say a dollar, 20 people voting on my post would make me happy. As it is, 20 people voting on my post gives me 20-40 cents (unless you're one of them! :P ). That means these small fish - these minnows - group together and upvote automatically in order to rise in SP. They look for ways to trick the system, in other words.

When we made @SteemDeepThink, we decided to use autovoting in order to promote authors, rather than content. So if we judge an author's content to be good, we vote him in, and automatically upvote his posts. We each read some of these posts, and if the quality drops, we reevaluate our vote (every new member can vote). The goal is to help the author rise in SP so that his vote will be worth something, giving him our votes when it matters, simultaneously, which might land in him in 'hot' territory. There are authors that I know will post good content without fail, and so I upvote some of these authors automatically, and then hope I'll read some or most of their stuff when I have time. Your posts have a certain consistency in their quality, and many of them are good earners, so I'm not surprised you're an auto-voting target! It's easy to be cynical and think they're after the curation reward, but I think many of the auto-voters might actually enjoy your content.