Parents should carefully monitor how their children use smartphones.

That's pretty much the same problem in every other country where smartphones are popular.

... so they arrest the kids, but what about the adult buyers? Aren't they focusing on the wrong people here? These kids wouldn't be selling if there weren't buyers out there, and frankly I'm far more worried about someone prepared to buy the services of an underage prostitute.

And you'll probably find that most of the girls "soliciting" are just putting their profiles up to see if men out there think they're pretty enough to make an offer. I doubt whether more than a small percentage would actually go through with the transaction, so one has to wonder whether this can legitimately be called "soliciting" rather than simply "teenagers wondering if they're pretty in the age of the internet".

I'm not saying that its a good idea for girls to do this, just that treating it like a crime would be a lot like treating every punch-up between teenage boys like assault, it would be a huge over-reaction.