I don't see anything wrong with buying extra things, such as when Durnan's got the surplus from others who've sold it to him, if you're a new char or passing them on to other chars of mine (some I do NOT do this with as I like having a few to rp or just get through the old fashioned way
). But yah, I agree that using an amulet to run past everything and get the stones isn't my cup of tea. I suppose once would be ok if you never saw any of the lower levels and wanted to try 'em out or see how hard they are.
Heck, my only char with more than a level 3 stone is my fighter/wm who's approaching the upper limits of leveling and she got her last two stones by running through with others (thanks Wellard and Robertthebard!) and slashing, hacking and dying/respawning the old fashioned way, even though she has an amulet she found in her adventures.
Still, I guess it's an individual choice in how to play, but I WOULD say it's wrong for someone to clear out the stones on lower levels with a newbie char and an amulet if it means someone coming through the usual way won't be able to get one. That would seem really unfair to me.