I would love for someone from Riot to come to this thread and tell me that I'm wrong. Because I've been playing this game for 2.5 years and all the evidence supports my claims.
Until someone from Riot tells me otherwise, I firmly believe that this game rigs certain matches for or against you, depending on your W/L ratio and how many games you've won or lost in a row. And they do this to make it harder for you to climb, so you spend more time playing their game.
Edit: And I also believe that they use their report system to help skew games. So when someone AFKs and you report them, all you're doing is ensuring that that person ends up on your team when you've won 5 games in a row and you're in promos. (And to all you dumbasses out there who would take this literally, I'm obviously not saying that exact person will end up on your team, I'm just trying to help you understand).