How are most currencies on Earth accepted by only a few people??? Most of them are universal at least within the borders of the issuer, and can be traded for other currencies. Not so with Bitcoins, it seems.
They've already posted links to exchanges.
And no one here is denying that Bitcoin has the same challenge any new currency has, which is acceptance. However that is also the point, it's also the same challenge any new currency that's ever been introduced has also faced.
You seem to have some kind of mental block somewhere that money has to have some fundamental level of "reality" or "officialdom" in it's issuance. Even gold or silver has to have some sort of value in the minds of those who mine it, trade it, or hold it.
If everyone is starving, and I have the last loaf of bread on Earth, all the gold in Fort Knox is worthless. This is a fundamental risk and challenge any medium of exchange ultimately has, no matter what it is. In this, all currency is equal. Where they are not equal is when and how they suffer these risks, if ever.