I tried deleting my Dwolla account right after TradeHill went down, but couldn't for the life of me figure out how to do this. I posted a question on their Facebook page asking how one goes about deleting/cancelling a Dwolla account, but it was never answered. So if I understand you correctly, you have to contact their customer support to ask for your account to be deleted? Wouldn't it automatically be disabled if you haven't used it in more than 30 days?
It would seem the fastest method is now to post your account number in this thread.
Dwolla account ID # 812-665-7282 has been suspended.
Oh well. At least my account was empty.