Ok, i will concede that the autor does have a point, however, i'm not entirely enthused about his suggestion. WoW does affer an XP boost to toons that have been parked in an inn/haven't been played for X amount of time (the longer X is, the longer the xp boost lasts): that is pretty much the limit of what i'm comfortable with. What the autor is suggesting is Power-Leveling lite: you get something for essentially doing nothing. Is that as bad as buying a max level toon from a third party farming company? No, but imo it's in the same ballpark.
I think the root of the problem is holding a player' interest, and the majority of complaints that i see relate to a redudant nature in the leveling process. I think that a better solution would be to come up with gameplay that's more dynamic and offers the player more interesting options on how to gain xp.