The actual reason it got popular, which a lot of other people in this thread have mentioned as well, is because it was much faster than MMS because the photos were low quality(and at the time I don't think Apple had introduced iMessage), and the photos didn't stick around on your phone after they'd been sent, so it was perfect for sending silly/mundane things that don't need to be preserved.
edit: I seriously don't understand how you immediately jump to that being the new functionality when sending payments today is as simple as logging into paypal or any numerous other payments sites.... Not to mention the age requirement of 18? This comment is just fear mongering.
I can, however, see someone asking for cash through the very same app that they're using to send nude pictures.
I agree with the GP, this is gonna get interesting.
Can you identify a similar set of circumstances where this has been successful for more than a brief period?
But I do expect some scrutiny due to the oh-so-popular puritanism Americans hold in public life towards sex (both democrats and republicans) yet largely ignore in private.
Do you think teenage girls and boys are really going to start selling their nudes? Just on a shallow examination of this possibility, it seems exceedingly unlikely to ever be a problem on a scale larger than a handful of cases. The social aspects of trying to sell "nude" pictures of yourself would be utterly taboo. The only market would be for people that you don't know, yet then the risk increases dramatically. There are already 100s of sites where they can do exactly this (pretending to be 18), yet its not happening, at least on the scale that the fear represents.
All it takes is a "handful" (or less) when child porn is the subject. I wouldn't go anywhere near money transactions given the risks.
I'm not suggesting that it will be frequently misused -- but even one mishap could seriously harm their business. Law enforcement takes child pornography more seriously than just about any other offense, and money on the table makes it even more serious.
If you are speaking about adults selling pictures of abused children back and forth, this'll be no different (even less secure) than current technologies that pedophiles use to avoid detection.
Can under-16s not get debit cards in the US? I know they can get them here in the UK, I got one when I was 14, IIRC.
That said, I don't know if there are regulations here in the US concerning debit card age requirements, but from a cursory glance of a few US banks, it looks like children under 18 are allowed to get a checking account (and hence, a debit card) provided that they get a joint account with their parents. Perhaps the policy is different for teenagers who wish to separate finances from their parents for whatever reasons, but those are edge cases.