ARAM Dodging
At least during night time on the east coast, I tend to see a large number of ARAM dodgers. Whether due to their inability or unwillingness to play the characters they are given, they leave the game and forfeit everyone's randomized champions.
I regularly see 3-4 dodges in a row before getting a game that everyone stays in, meaning sometimes it can take longer to get a game than it does to play one, due to the cumulative wait time between queues, champion select, and eventual loading.
I'm of the thought that scaling bans should be implemented - if an account is seen to regularly dodge a queue (for any game mode, not just ARAM), it should go from 15 minutes, 1 hour, 1 day, 1 week, and finally suspension. This is just an example of sorts; I'm not sure what system, if any, is currently in place, and we can't tell who dodges due to the generic "player has not selected a champion" or "player has left the game" messages.
There doesn't appear to be anything in place to prevent these individuals from creating multiple accounts and simply hopping between them in order to further dodge the ban cycle, though. I'd be interested in hearing if Riot has observed this behavior, and if they have a plan to act on it.