I overall like ARAM a ton, and I don't expect ppl to know champs very well, and I almost never complain about people on my team while we are still playing, but I actually got really mad at this Anivia on my team, enough to say something (but it was only "dammit, stop blocking me").
I was Volibear, in the bushes a lot, ready to charge into their TF or Quinn or Ashe (whoever was closest) and Anivia blocked me with her walls....again and again and again. It happened about 5 times before I got really upset, and it was a bit embarrassing how mad I got (I'm laughing about it now) but I reported em. I don't think I've ever reported anyone before for things that weren't an attitude/chat problem.
It was bad enough that most of the team would go after Garen first (especially our "pro" Diana who explained that "if we attack Garen first Quinn and them will give up and run away"), but to be denied on a regular basis when one of the carries finally got bad positioning...I could have spat at that Anivia.