Don't leakers generally initiate contact with reporters? You raise a good point (eg whether people who would be committing a crime by revealing classified information might feel chilled), but I think you're overstating the severity of the effect. If I was working with classified material and someone approached me as a reporter soliciting classified information, it would be part of my job to suspect espionage and report the contact. Instances of legally privileged rather than classified information would be broadly similar, possession of privileged information usually involves some sort of fiduciary obligation towards the person who entrusted you with it.