I like to do all the auctioning on a bank alt. In another game, I once got up to 645 items up for sale, basically entirely as a result of playing a whole heck of a lot (I was on vacation) and sending all the loot worth selling over.
More auction slots = more healthy market.
And whaddya know! You could make money at it! I'd be pretty happy to buy account-wide 5-slot upgrades.