How would you ever check the age of members? There's plenty of mature teenagers around, but even more immature adults.
let me just ask you this what would you gain from lying about it ? Besides being able to play beside the glory that is me (cough cough) and maybe a few older players.
And yes there are many immature adults around, seen quite a few up till now and most likely i will see plenty more. You could even say some are more immature at older age then when they where younger.
With that said i should say i'm not even that mature since here i am typing stuff to create a guild in a game. The thing i "feel" to old for is too compete at the level that the game frustrates you or discuss it in that manner. I'd rather have a laugh while dying then get screamed at by somebody who thinks his life depended on it.
The people i was aiming this at where the stray housedads that found there way to this game somehow, or the 20 + that just go there way but enjoy conversating in the guildchat at times. By the looks of it it's not going to happen anytime soon, but gonna keep my hopes up the game is still very fresh