I had someone on my friends list that added me after we had a good game. We proceeded to win the next 3 games, lost 1, then won 2 more, which put me in Gold for the first time. After that, I was worried I'd fall, so I stopped playing ranked on that account for a while, but would play normals. The person later said, "you're just using me."
Um... didn't you add me? Didn't you ask me to duo, friend, and invite me to a lobby instantly after we won one game?
People are just strange. You have one pop off game, and instantly they think you must be a smurf or something. Yeah, sometimes I'm really good, and sometimes I'm REALLY bad. I had one game as Zilean where I went something like 3/0/19, flashed to ult someone dying to ignite, and managed to steal first infernal drake by randomly QWQing over the wall with no vision. The next game on Zilean I went 1/8/4.