I was at the university book store today, buying pens and other gak i needed. As I walked down the stationery isle this caught my attention
Picture hanging wire. So i bought it and tried it out. ~$3 for 15 feet really isn't that bad. It doesn't quite have that convincing look of barbed wire/razorwire, but it looks convincing enough to do the job. it's pliable, holds what form its put into... Compare that against $5-8 for, say, army painter's razor wire which gives you only about 8.3 feet of material. One certainly looks better, the other is cheap and doesn't cost you any labor....
figured I'd throw it out there.
I know there's also the possibility of doing it yourself using a wall-hook, two pieces of wire and a power drill. But that requires effort.
i wouldn't have bothered posting this but for the fact that I don't actually recall having seen this posted earlier.