See, I would never put a gift in some random box, because I would assume that the person would think that the gift was "whatever the box said". So these stories always surprise me.
Many items these days come in brightly labelled boxes with pictures, designed to show what is inside the box (because we often don't open the box before purchasing, whereas once upon a time we might have selected an item and had it boxed instore). If I see one of those boxes, I assume what is in it is what is in the picture! If I did have to re-use a random box for a gift, I would use a black marker to cover the name of the original item wherever shown. Of course, that would make the box quite unsightly, so I probably wouldn't want to do that anyway! I feel bad for the recipients in these cases, because unless it's a deliberate joke, how are they supposed to know that what they appear to have been given isn't what is actually in the box? Or is it a requirement of etiquette that we open the box itself and ooh and ahh over the item? The concept just intrigues me.
On a similar note, DH and I received 2 gorgeous bathrobes for a wedding gift. I didn't *love* the pattern, but I do love robes, and as I already had 2 robes at the time I popped them in the cupboard without taking the clear plastic packaging off them. When I actually opened the packaging and took them out (a year later) I was delighted to see how long and cosy they were! Far superior to my old robe. So perhaps I should have opened them at the time - the gift was far nicer than I'd ever imagined! But I considered "opening the present" to be taking the wrapping off and identifying the item, not necessarily exploring it completely.