Because of the potential for selective or punitive prosecution I'm in favour of legalising teen sexting. Obviously the law needs to be carefully drafted to avoid allowing child exploitation, but it should absolutely not be possible to prosecute normal sexually-active teens under child pornography statutes. “Trust us, we'd never use it against the people it's supposed to protect” isn't enough.
No victim means no crime. (Morally, I'm using the word "crime" here to refer to a moral crime.) But it also means that the prosecution of such non-crimes is itself a crime, meaning the "guilty" party here is the victim and everyone involved in their prosecution, up to and including the supreme court, is criminal.
Was it a crime? It might. be tempting to say no, but laws do exist as a deterrent.