This is a discussion, feel free to contribute your thoughts, but also say why they make sense.
Right now there are five bans per team and I don't expect that to change in the near future.
When I started playing lol I used to ban champs I was personally bad against. Usually I'd ban a supporter, when I played support myself. And that baned supporter would be my counter. Nowadays, as a jungler, I ban unbalananced champs like Kassadin, Pyke etc(Patch 10.1), I dont make my decision dependent on my role or what I'm playing or what my team preselected. I just ban the same few champs all the time.
Now I don't want to say that the game was ever balanced, because it was probably not. It might have just been me ignoring the meta back then or not realizing it.
But I liked it, when I could just ban a champ because it countered my champ or because I did not like him as a laning opponent, even if it was due to my own ignorance.
Therefor I believe that for good, meaningfull bans there needs to be a balancing that does not make you ban a champ(and therefor take it out of the game) just because he's generally broken. At the moment it feels like I have to use my ban to fix the balancing teams mistakes. And there are too many.
Edit: To clearify, I do not ban an unbalanced champ, when a teammate preselected him, but that should be obvious ;)