[sebbecai]

What makes these sites "hyperpartisan" is that they are directly funded by candidates or PACs that support them.

My read: it's in their interest to seem balanced until the moment that it matters--when covering candidates or policy.

[altcognito]

This is the answer in addition to the stories being more subtle in many cases than implied by the term "Hyper-partisan". While "subtle" seems to imply less damaging to the political system, much like many people complain the media lies as being a large issue, this is pretty much the same thing except with a super PAC behind it.

Someone else brought up Facebook -- that's the other thing -- these sites are typically linked or used as sources during election season.

I think the amount of sway these sites has is small, but moderately effective. In a day and age where 70k votes can swing an election in a country of millions, it is just one of many tools in the bucket of lobbyists and political parties.