brilliant! Everyone would win then
Blizzard could get money (and extra for the conveniance factor) from people who don't want to grind, and the people who are paying power leveling services anyway would go with blizzard since it would be official and no change of losing account from someone stealing the password or blizzard banning them.
The only downside I see is that some people would get upset at people with money gaining advantages in that way.
axed: They have a bunch of anti-bot security in WoW already. Including checking for stuff thats running while you play the game.
WoW has stuff that could be termed spyware in it to check you and your computer for bot software.
You can google for some details, people have done stories on this before.
Sepharo: Most capchas have been defeated to some degree already. You can google up news storys on it, but for instance I've read that hotmails can be defeated something like 30% of the time, so spammers can create emails to spam from.