I don't have any story about them, but I know the US has had similar problems with modern counterfeit operations, too, especially for those purchases made at convenience stores in larger cities and other non-postal facilities.
Since you have posted your question under "US Stamps" I thought I'd share this
ebay listing. Frankly, even with the clear indication that the stamp is counterfeit and must never be used for postage, I'm surprised that the stamp can be sold on the secondary market like this without postal officials making an issue of it.
http://www.ebay.com/itm/Scott-3635-...em4861e10b8d