Ok, so this should seem like common sense, but a couple we know has had their registry for a few months now, and their wedding is 5 months away. They have massive amounts of duplicates. On their registry, there are five coffee makers and two vacuums, two Calphalon sets, two blenders, two food processors, and two different sets of fine china. Also, there is like nothing under $100. Some of it is clearly being gift-grabby, and the ruder part is just being so lazy that they didn't edit their registry. I know their wedding is a few months away, but the save-the-dates are out and it's published on the internet. Seriously, remove duplicates and edit your registry!
Update: So we got the invitation to this wedding. On the lower left of the invitation is "formal reception to follow," and the wedding website elaborates on their idea of "formal dress" aka black tie optional. Sorry, no such thing as formal dress or black tie optional for a wedding... but at least they're only registered for two coffee makers now...