Thanks to my zaftig figure, I don't need to wear a belt. But I do buy them. Lately, whenever I enter my local Goodwill, I head straight for the accessory section. (Tip for Seattle upcyclers: the best Goodwill for belts is in Shoreline, on NE 145th.) 
Right now, one wall of my makeshift studio is devoted to belts. Most are leather, with a few mod plastic and hippie denim thrown in. I confess I'm drawn to grommets and rivets. (And I'm waiting for a very special bag to use that multi-colored leather beauty in the middle.)
At first, I felt a little funny buying and using leather belts. I'm a vegetarian, not a vegan, but I still don't like the idea of animals suffering for fashion. My rationale (rationalization) in buying second-hand belts is that, by extending the life of the belt, I'm helping make sure the cow didn't die in vain. Is that wrong? Am I fooling myself? Of course, I also love the feel of leather, and I know it makes the bag just a bit more classy.
Another use for second-hand belts is as cuffs. I bought this very cool cuff at last summer's Urban Craft Uprising show in downtown Seattle. It's made by a local company called Greenbelts.
Here's my version (just for fun). I found a plastic kids belt with a rainbow of butterflies. It was easy to cut into 3 sections and then add snaps. I gave one to my favorite 7-year-old, and she seemed to like it.
Again, my ethical dilemma emerges: is it wrong to chop up perfectly good belts just to remake them into products to sell or wear? Would someone else use them as a plain old belt? Am I overthinking this?