Let's also remember that it's not incredibly hard to trick a human. (One of my favorite videos related to counterfeit currency is Derren Brown paying for things with blank paper http://www.youtube.com/watch?v=3Vz_YTNLn6w (And if you think he faked it, he's still managed to trick a lot of other people otherwise.))

I wonder how much in total method after method of trying to stay ahead of the Big Money counterfeiters has cost? Mathematical solutions to the problem of forgery have existed for quite a while, I wish there was more a push for those. (And I'm not necessarily talking about bitcoin either, it's just one of many possibilities.) Of course even just going digital for everything would probably solve a lot of problems, and there are math solutions to keeping different types of anonymity as well.