This is a very easy way to make large amounts of gold/valuable items in less than 5 minutes. As far as i know, it's unbanable.
Anyways...
If you've ever been in a guild that you've left on bad terms with, were an officer in and got backstabbed, or just wanted pure revenge, and you knew the other people there pretty well (their personalities, the way they type, their freinds etc), this is a great way to ruin them.
Step 1: Roll an alt
Step 2: Level said alt to 10ish
Step 3: Whisper one of the guild leaders, and say "Hey, it's *insert officer name here*. Can you shoot me an invite?"
Step 4: usually they'll give you an invite, promote you to officer alt, and leave it at that. GET TO A BANK AS FAST AS POSSIBLE (It helps to park that toon near one).
Step 5: Take everything you can out of the bank, send the items/gold to your main, delete the alt, and enjoy