Yeah cause internet access and a modern computer are waaaaay more common than bank accounts or prepaid credit cards....
Digging around, I found they're almost equal actually, and cellphone users vastly outnumber bank account holders (cell phone users exceed toilet access !!!).
50% of adults worldwide have an account at a formal financial institution.
60% of adults worldwide have internet access, with 39% having home internet access (the remainder having shared or limited internet access).
80% of adults have cell phone access.
Sources:
http://en.wikipedia.org/wiki/Global_Internet_usage
http://www.gallup.com/poll/159815/home-internet-access-remai...
newsfeed.time.com/2013/03/25/more-people-have-cell-phones-than-toilets-u-n-study-shows/
According to wolfram alpha, there are 1.871 billion children age 15 or younger: http://www.wolframalpha.com/input/?i=population+under+15
Those 1.871 billion children literally determine the future. And all of them can currently use bitcoin for buying anything available via bitcoin. That includes Humble Bundles, for example, not just drugs. Though admittedly they'll still just pirate most videogames rather than buy them. But they won't be able to pirate MMO's, and it's a matter of time before MMOs begin accepting bitcoins.