The real wow hacking is...

when someone writes a freeware server, which is already done and even fixes the bugs the original game writers never did. Extending the possibilites by adding higher limits is imho a good thing also.

On the other side, wow is as basic as you can go. Only 6 quest types, no object collision (terrain collision is client side like movement) and only affecting the controlled object. (mobs and pets can go on slopes where a player can't as long as the player doesn't directly control them). Wow is a classical mud design with a 3d interface, much like diablo used the game engine of the freeware game nethack.

Btw, a good mmorpg always checks movement and line of sight on the server side. But that would need bigger hardware -like a real cluster- used in mmo-s like second life or neocron.