As a consequence of the global economic crisis, many European contries are now involved in taking strong measures to decrease the heavy tax evasion that is deemed as a majour problem for the health of national economies. A succesful initiative taken in Italy in this line has been to crowdsource tax evasion crimes through an iPhone app (http://tassa.li/) that allows customers to report when a merchant (from a bar, shop, restaurant, etc.) did not release them the till receipt for the purchase. The result is not hard to guess:
where 12013.57 is the amount of Euros that have been evaded according to the submitted reports.
This app is contributing to create an entirely crowdsourced map of tax evaders and is being acknowledged by the Italian fiscal authorities as a very effective tool against tax evasion. Of course, this also bring about issues concerning the trustworthiness of the reports and their verifiability and addressing these problems would fulfill the full potential of this technology.