Mojang clearly stated in it's new contract that players cannot edit files of the game, so Basically speaking, they've out ruled mods and some hack clients! I think that that is very unfair for the people, and isn't a very wise decision for Mojang. One reason because of that is because half of minecraft's players use mods or hacks and that expands players use of Minecraft. This also means that Notch's promise to make a Mod API is also probably a lie. Also it is very annoying in various places like editing names of items and the text when you go back home thru an enderportal. I would advise Mojang to remove this serious mistake immediately and/or make an adjustment to the contract.