Queued with Reported Teammate?
I played an ARAM and one of my teammates was a very unpleasant person. He cursed at all of our team and especially yelled at me because I was doing pretty horribly--granted it was my first time playing that champion. After over 25 minutes of this asinine nonsense and a loss, I reported him for unsportsmanlike conduct and went on my way to the next ARAM.
I clicked accept and lo and behold, that same jerk turd player was on my team. Luckily, since his head was clearly up his butt the previous game, he didn't recognize my summoner's name. I played much better, so I didn't have to suffer from hearing his whining and griping.
There needs to be something in place where if you report someone, they shouldn't be matched up with you in the future. Maybe being blocked from being matched with you forever is unrealistic, but even for a 24 hour period would help said jerk turd negative player reset their behavior.
TL; DR: If you report someone in a game, that person shouldn't be put in subsequent games with you.