People 18 and under are fine as long as they don't act like little babies. I've run into 10 year olds who are very mature. then I've run into those people who claim to be 16-18 who act like they're 5 years old.
It's more about their level of maturity than their age for me.
I'm personally 13, and I'm trusted as an admin over a 25 year old woman. Minecraft doesn't have an age limi. It's not rated by ESRB and if it was it would be given E10+ at the highest, and this makes it a bit stupid to be discriminatory towards younger users.
~Eragonski
It's more about their level of maturity than their age for me.
Young kids only bother me on games with voice chat when their voices are soooo high that my ears want to bleed.