Cryptocurrencies have captured the attention of investors and world governments alike, especially given Bitcoin's meteoric rise over the past 12 months. Cybersecurity expert John McAfee believes they may encompass the sum of all fears for governments the world over. The blockchain technology that cryptocurrencies like Bitcoin and Ethereum are built on helps to solve the problems that plague traditional banking, by cutting out the middleman, thus reducing fees for consumers, while also decentralizing and securing transactions. With no centralized exchange to control or influence, national authorities around the world will find it increasingly difficult to determine a given citizen's income and thus their income tax owed, undermining a critical source of government revenue, according to technology pioneer and head of MGT Capital Investments John McAfee. "Our income taxes are the greatest source of revenue, but if everybody's using Bitcoin, the government doesn't know what your income is.