(a) is a valid product of journalism; (b) probably isn't.
We think (b) is, though, because one way that media outlets secure power for themselves in the market and elsewhere is by exploiting (b) to inflict punishment on the targets of their stories. They don't like Anthony Weiner (no surprise), so they're happy to torture him to get extra pageviews.
Most of us would probably agree that paparazzi publishing pictures of celebrities naked in their back yard with telephoto lenses is not okay. Publishing pictures of Rob Ford smoking crack? That seems more than reasonable. Publishing pictures of Rob Ford smoking crack, naked in his backyard? I don't think that Rob Ford's attire changes the situation (does it really matter if he's wearing a t-shirt, a business suit, or his birthday suit? Either way, he's smoking crack), but how do you encode that in the law? I am not convinced there is a good way, even if we just say "lets hash it out on a case to case basis in courtrooms, then you have to consider SLAPP concerns.
I don't know. Like you said, it's not simple.
But the fact that it's not simple gives lie to the idea that persecution of revenge porn sites somehow impinges on the civic function of "journalism".
I'm also not sure I trust the media in the role of verifying and then hiding evidence. Far better to just do full data dumps and let us figure things out for ourselves.
As a basic example, someone who is a "normal person" might have a photo leak that goes so viral the photo leak itself makes them a "public figure" by the old celebrity definition. What then?
Is pax dickinson a public figure? How about joe the plumber? Both have been the subject of journalistic investigation.