To give some perspective on what may be a useful amount for a global currency: there are about 100 Trillion (100,000,000,000,000) Japanese Yen in circulation. And that is just one country's currency.
And there are over 10
9 Japanese, that gives roughly, 10
6 Yens per person.
That means nem would need no have 400,000 users. (Which is possible, but most probably not in 2014

)