Sometimes on the WoW forums you'll see a post that goes something like, 'ReRoll guild starting up on server X, come play with us' or something like that. What reroll means is that they are going to start a guild from scratch, everyone starts at level one, and there might be other rules. So everyone levels up together, runs Deadmines, Scarlet Monastery together etc.
I'm not starting a guild, I'm just curious. I don't think I'll buy WoD even though my resolve is weakening.