I went in to my local Gamestop yesterday to check out their used games, and all their Nintendo DS games were gone. I asked the manager about it, and he said due to other Nintendo games (Wii, Wii U) they were asked to remove their display for Nintendo DS cases.
All cases were going to be thrown out and the carts *only* would be kept in those stupid dinky locked display cases.
The manager thought it was ridiculous as well (I mentioned that the 3DS can play all of those games easily!) but said that he'd let me know when they were getting rid of the boxes (they still had them in drawers for the time being) so that I could go through them. If he lets me, I might just try to take all of them and deal with getting rid of them later.
Anyway, just a heads up in case they're doing this as your local shop, too! It doesn't make any sense - the DS was such a money-maker for them... why would Nintendo or Gamestop decide to pare down the display so drastically? (This store still has boxed PSP games, btw.)