A fair point. I guess I feel as if he had some sort of responsibility to let his potential sources know about these risks, but didn't because it wasn't in his self-interest. That's actually exactly what he says, come to think of it.
I think the OP is assuming that it would have been common sense to do so in the first place and they are assuming the journalist was just too lazy to take that protective step.
What? It is pretty clear from the article that his response was to change his e-mail provider.