This is lame to pull on your main.
Your rep will go to shit, and word of mouth blows in WoW commerce. I tried to using the same character to scam like weeks after I had last used him and people were screaming "You scammed my guildy!"
Lest we not forget the good ole Add Friend button. I always add people before an instance. I have like ten people in my friend's list I will never run with again for ninjaing. What's to stop this dude from at the least, remembering your name and spamming you everytime you log??
So by the time you level multi-alts to do this without catching hell, you could have a toon to 70 and be making more gold than you need.
Rodo