Bot Players
I think that this is kind of a growing problem with League and that there really needs to be an automated way to distinguish between real players and bots. The tribunal system clearly doesn't do anything to solve this problem because there has been a growing number of bots playing on TT, not shrinking.
In my opinion, a bot is worse than a bad teammate because it's a foregone conclusion at the beginning of the game, but you're FORCED to play lest your own account get punished for being AFK. It's wasted time for anyone on a team with a bot, and wasted time for anyone playing against a bot.
On the technical side, this really shouldn't be that difficult of a task -- Google's new CAPTCHA claims to be able to distinguish between people with a single click of the mouse. If the League servers could come up with some confidence level of whether or not an account was using a bot, they could pose a CAPTCHA to the account of some kind and if it fails, the account gets a penalty. At the very least, there needs to be SOME measure in place against bots.