It's been a couple of weeks since I've been on Amazon and even longer since I've been on someone's wishlist (other than my own around the time of my birthday).
I was very pleased to see a new (Ian tells me it's been there for a few weeks) button next to "Add to Basket" for each item on the wishlist: "Buying this gift elsewhere?", clicking on which gives the following message: "If you decide to purchase this gift somewhere else, you will need to reserve this item to keep others from buying the same gift". I'm not sure what reserving the item actually does, but if it also removes it from the wishlist then that's good enough for me. Now if an item is out-of-stock or over-priced on amazon it will still be possible to buy it for someone without having to tell them you're buying it and asking them to remove it from their wishlist. Hooray!!