The above is a link to a Blue Post from a Blizzard rep. explaining how skipping content in this fashion ruins the game.
Emphasis mine.Technically speaking, if we wanted gold selling or even power leveling to be permitted we could offer it ourselves. After all, we control the virtual currency and we have control over the characters.
We do not because we value the integrity of the game and therefore there are certain activities that we prohibited because we feel it is damaging to the game and game environment.
The sale/purchase of gold inflates the market to where nothing is really worth anything. So a low level green item could go for 20k, because the 20k is not worth much.
As for Power leveling (meaning someone plays the character for you), there are many in-game and promotion related options available to help you level, to get a friend into the game, but much of it still needs to be done by you.
People play games, especially MMO's for different reasons: story progression, PvP, 'end game' raiding, social interaction, but there is very little value in any accomplishment if it was simply handed to you.
The simple fact is these practices go against everything we stand for as gamers and frankly that is what it comes down to. Blizzard Entertainment is a company of gamers who create games for folks like us. Gamers.