I think IKEA advertises it as a wall divider, so I think it would be ok, probably even the 5 high one. If not, you could downgrade to the 4x4, which I think would be definitely ok (assuming children do not climb it). I was just at IKEA two days ago, and have only skimmed the 2010 catalog, but I know they have a photo of Expedit in the first 10ish pages as a room divider; it's definitely the 4x4 or 5x4 and is in one of their "room scenes" (i.e. not just a photo of the item, but it in a whole scene.)
Advice and commentary on living overseas
DD1 15, DD2 12, and DS 9