Amidst the technical issues plaguing League of Legends' World Playoffs, there also emerged accusations that some of the contestants had essentially "cheated", by using the venue's monitors (there to show the game to the large crowd) to check in on the activity of their rival players.
After an investigation by developers Riot Games, a number of contestants were found to have engaged in "unsportsmanlike conduct" and were issued strict warnings against future violations. This was mainly due to the fact that, while they were caught looking at the screens, they hadn't actually gotten a competitive advantage from doing so.
One player in particular, though—Woong, from Azubu Frost—was after review found to have gained a clear advantage in his team's quarter-final by looking at the big screens. Riot also found that Woong's teammates "modified their gameplay based upon the information" he gained by looking at the screen. As a result the team has been fined $30,000.
That'll be of little consolation to TSM, the team he defeated, but since members of that team were found to have looked at the screens as well, they can't complain too much.
In relation to why the quarter-final isn't being replayed, or why there were no team disqualifications, Riot claim that AzF's cheating, while a violation of the rules in of itself, did not decide the winner of the game.
World Playoffs - Rule Violations [League of Legends]