The power users do, moderators do, those obsessed with reposters and bots too but I don't think the majority cares enough to check that. Most just follow the initial votes, so if the users who were early decided it was worth upvoting the rest of the people will generally just follow along. I think that's why selling votes is also profitable, you can get your post to the frontpage if it is good enough and you bought a few hundred early upvotes.