After five straight years of exponential growth, Bitcoin should have earned the benefit of the doubt by now. After one year on the market, it's value went from fractions of a penny to $0.05 USD, which is borderline infinite ROI. The next year, it rose to $0.30, only a 500% increase in value. Good luck getting that anywhere else. 2011 saw BTC rise to over $6 USD, which was just scary growth. The next year, it only doubled in value, a real "off year". 2013 was a rebound year, and it finishes up at almost $800! Mind you this was mostly because of the Mt. Gox Bot Buying Bubble, and the Chinese market having free reign at an initially unrestricted BTC market.

For thousands of years, gold has been the international currency, and for good reason.