if you are at my low level of elo, then you probably see four tanks banned every game, since people at low elo cannot handle tanks in teamfights. There is some brain disease prevelant at my elo that makes people blow all there cooldowns on the first champ they see, which is almost always a tank.
I'm serious, the loss most often goes to the team that with a squishy that runs in front of the tank most often.
I've seen (and been on) teams that were successfully tanked by full tank build Mordekaiser. No matter how many times you tell people to just run around him and hit the squishies, they just stop at morde, blow all cooldowns, and have no clue why they are losing (often blaming their tank for not tanking. Irony is awesome, isn't it?)