Usernames to lowercase

Whereas it used to matter regarding case, now http://skins.minecraft.net/MinecraftSkins/userName.png does not care.

By converting the username to lowercase we prevent it from being cached multiple times when it is entered differently, and also we reduce the number of unneeded requests to Mojang.

I'm not sure how much of an issue this is for us, but I can't see major any negatives?