First, I'm going to say that I trade in the USEast Ladder forums quite often, and I've met only honest, straightforward people in doing so. I've drop traded with several and muled while they held games for me and vice versa.
However, in the many trades I've either made or seen posted, I don't think I've ever had the origin of the runes be part of the discussion. If I were lucky enough to find a perfect Maras, for instance, I would expect to get several ists for it. I don't think I would ask the buyer if he personally found or cubed them all, because in all likelyhood, he didn't. Is that going to make me trade it to the guy who offers 3 and swears he found them all rather than the guy that offers 5 and traded for some? No. I'm going to trade it for 5 and take the same chance he did that they don't disappear. And more than that, I'm going to trade one for a HoZ, and whoever gets it is going to be taking the same chance again. It is sad that the chance the ist is a dupe is part of the trade, but it is a part of life on bnet.
And back to the original post: there are threads in these forums about items vanishing everyday, including one about 2 posts down from yours as I write this, and one I was going to link to but can't find reguarding 3/20/20s poofing (probably deleted.) I doubt all of those items have been held in storage since the latest dupe-proofing, so I'm going to assume that dupers are alive and well, if not as numerous as before.