I posted in the bug forum that the non-saleability of bags is misleading, given that you can evidently auction them. There needs to be some in-game information on what can and can't be sold; players shouldn't have to come to a forum (especially one like this, which is currently very difficult to search effectively).
The option to view listings of bags in auctions is the part that's a bug, I believe. There was a similar one with elements not that long ago. I keep my old bags for storage in my house -- you can fill them up and stick them in the cabinet! I have given some as surprise gifts for new players as well though, it's a nice way to welcome them. =) Bobby, you are right that there needs to be something in game that tells people though, it's a question that also comes up quite often in chat.
Bags for beginners is such a nice idea! When I was first starting out, I found a generic bag full of gems up in a tree & it was such a nice surprise - it was both helpful fiscally & it gave me such a good impression of the glitch community. I'm not yet in a position to give away bags of gems, but I delight in leaving food items in little nooks and crannies across Ur :)
I hadn't heard of leaving them around -- this was the first bag I got rid of -- but I'm now putting items in bags and leaving them around regularly and I'll never sell one now.
Note: It may be allowed to auction bags, but it never worked for me. The auction screen wouldn't let me select the bag as the item to auction.
It might be a good idea to leave a note with the bag, since otherwise you're teaching people that "if it is on the ground, it is free and for you." I think that ambiguity is what leads to new players getting confused, and then in trouble, when they see things on the ground and assume they were loot, when really they belong to someone.
@Pomegrandy: I agree that putting a note to be clear would be a good idea, but I thought things on the ground were considered fair game? I can't really think of why you'd want to drop something you meant to keep out in the open (outside of your house), unless it was an accident...
I sometimes drop bags when donating to shrines, in order to donate a specific number of items to get me almost all the way to an emblem (but not quite.) Occasionally that means I've got 9 or 10 bags on the ground at my feet, and I'm always a little nervous that someone is going to come along and scoop them up before I can reclaim them. I've also done a little bag rearranging in public spaces before, which can leave items on the ground for a minute or two while I get sorted.
In both those cases, though, I am always standing right over my items while they are on the ground; there is no question that they belong to me. I would never drop something, wander away, and expect it to still be sitting there when I got back.
Inventory full while cooking, mining, spinwheel winning, etc. Accidentally dragging thing out of your inventory, missing a shrine or a person when an item is let go, are a few of the reasons I've accidentally dropped items...