Yep. Facebook does that too by the way. Twitter isn't quite as bad.

I get very confused on them. They go by the marketing logarithms - most commented on, or most liked or most popular gets on top. It's a popularity contest. So the more people who comment or like a post, the more likely you will see it. And since negative advertising or negative posts get the most attention - you end up with those, or you get the ones in which folks are promoting stuff people want.