When Bernanke print USD, he doesn't hurt EUR or JPY
Are you really sure about this ?
The reality shows that to keep the economy going if one major currency is devalued all other must be too. Don't know why, probably because it creates a huge imbalance in trade and business competivity.
That's just due to stupid mercantilist believes of governments worldwide. When the dollar devaluates, they devaluate their own currencies in order to subsidize their exporters (at the expense of the rest of the society, but don't expect them to understand/care).
But what grondilu said is only applicable to national currencies like government currencies, which have their own market. USD doesn't impact EUR because mostly they are not used by the same people. An international alternative to bitcoins might take part of its share if it's really better than bitcoins. Simple clones wouldn't.