There are lots of imaginative people running round in the world.

I have personally found stilletoes and small caliber guns disguesed as ballpens.
Once I was almost shot by a fake cellphone which turned out to have 3 oneshot barrels inside.

As to wether razors are used as described. I have no clue but if it is indeed used in jails. then it would stand to reason that the same persons would also use it outside as they will then be familiar with that type of weapon. Being the smartest thing or not. Personally I think its a dumb**** method, and I agree with monji and KF that your more likely to hurt yourself then others.