The business card is still an essential tool to have these days, never mind that you already change your smartphone with each new model that comes out. After all, social networking accounts and micro blogging sites have also become as essential as your calling card, so to not have a Facebook or Twitter account might be a bigger crime than lacking a business card. Well, someone didn’t get the memo (good for him!) and decided to come up with a circuit board business card that relies on the persistence of vision phenomenon to display his name, phone number as well as website address. The card can be manufactured and cobbled together for around $2 a pop, but to have it mass manufactured? We don’t think this will happen anytime soon. A pretty neat hack, but not exactly the most practical, although it might probably be the one that leaves the biggest impression.