Well you have your four types:

1) WTF, HAXXX, DUDE, REPORTED type. just ignore them. it is a waste of time to deal with them. The best thing is to do absolutely nothing as anything you say will just make it worse.

2) HOW YOU DO THIS, WHAT MOD ? types. I usually take the 30 seconds to explain that I have 5 accounts and tell them if they are REALLY interested they can go do www.dual-boxing.com/forums2 to learn more.

3) friendly/congratulate types. Most often these are people that dual/multi box themselves or have done so (or have friends that do). I usually have a quick chat with them and if they want to know more I send them to this forum as well.

4) Very polite people that try to explain to you that you are violating TOS. I just roleplay with them. It REALLY confuses them.

Also on alliance side do not bank in Stormwind or Ironforge. All the gold sellers make those stupid level 1 characters that spam people with /say in the AH and bank there and everyone is really annoyed and has extra low tolerance. I bank in exodar (mage portal), especially since I am revered there so regents/repairs are cheapest. Few people and much more relaxed attitude.

Ziran