Rev 13:17 And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name.


My friends and I actually had a discussion about how Bitcoin could cause this to happen, but BTC wouldn't be the  mark, but rather the government would create it to fight BTC. 

If everyone started using BTC and therefor no longer had to pay taxes or even created a tax problem because it's impossible for the government to find out what you owe, they could then say, Hey you can only buy with USD or go to jail.  This in essence would fulfill the prophecy.