Nah, if someone's not a pro, that's fine, I have never banned a newbie to date (newbie, not noob). To ruin a game for me usually they have to try hard. An example would be in DOTA and they give items to the other team, or let themselves be killed numerous times by the other team, things of that nature. Thus runing the game for me, in that it is not possible to have fun.
I used to just use a piece of paper to write down their names, but now I use this, and it's easier, but either method would work for me.
I almost always give people a second chance, sometimes a third. They could have just had a bad day or whatever.
I am sure that you could abuse it as well, and I have seen it, but that can generally be done with any system.
EDIT: I forgot to add that I have only banned people from DOTA games, nothing else.