Quoted from Sparky:
You two wouldn't make very good jurors.
I wouldn't want to be. But my brother-in-law is an FBI agent. He has told me a lot about how they pursue these types of cases. False arrests aren't very common when it comes to child pornography. Sometimes it's not what you think, but it's almost always something.
The definition is broad though. Someone can ask for a nude from someone they think is 18. If they send and they're really 17, you can be in trouble. That's considered possession of child porn.
Obviously it can be much worse, but they're not coming to your house with a warrant unless they have very good reason.