Buy It Now
I think this is an over-site but when an ad is set to sold, the Buy it Now link still appears and it still works. I think the link needs to become disabled or should not show if the item is no longer available. I haven't try it on an expired ad yet, so you may want to also check that too.
Question: When someone uses the Buy it Now link and completes the payment, does the ad status change to sold?