Theft is taking with the intenetion of permanently depriving the owner. Value is not relevent or even mentioned, so yes you can be charged with stealing something that is worthless. Anyway I would dispute that counterfiet goods are worthless, they may well be for the purposes of certain legal processes but they do have an intrinsic value. Also if you think about it there are lot's of things that are worthless to a thief but priceless to the owner. Value is subjective.