Cryptocurrencies don't make sense as general currencies because they're deflationary. Currencies need a lot of liquidity to be the grease for the wheels of commerce. It doesn't make sense to pay salaries in a deflationary currency, as people are more inclined to horde than spend. You need a currency with slight inflation but we all know how easy they can be corrupted by printing too much and triggering higher inflation, or printing even more to finance government debt, leading to even higher inflation (wink, wink Federal Reserve).
If "deflation" for you is the increase of purchasing power of a monetary unit (as opposed to the decrease of the supply of those units), you might want to consider that such "deflation" was pretty normal in the US before the FED started it`s management:
http://en.wikipedia.org/wiki/File:US_Historical_Inflation_Ancient.svgSource:
http://en.wikipedia.org/wiki/Deflation#In_the_United_StatesI would not agree that we necessarily need a currency with "slight inflation". The finance industry (where I work) needs it, because they want to sell products for people who want do defeat inflation. It`s funny that buying such products is called "saving", whereas simply putting aside a monetary unit for later because it is gaining buying power is called hording.
