Bitcoin can be seen as a sort of digital gold. Credit cards / Paypal / etc. could work exactly the same but be backed by Bitcoins instead of USD. See http://undergroundeconomist.com/post/36076277512
Funny you should mention gold... remember all those "digital gold currencies" in the early 2000s? And how they were used in all kinds of frauds and scams?
A business opportunity whichever way you slice it.