I've been somewhat ambivalent about the idea of journalists having special immunity for a long time. On the one hand, I think that it's pretty important that anyone who has information that may be relevant to a crime should reveal it; getting the facts about crimes is important enough to society that it seems justified to impose a penalty for withholding information. On the other hand, it is a sad reality of our society that are cases where powerful people have secrets that it would be in society's best interest to reveal, but the would-be revealer would be taking a serious personal risk to little personal benefit to reveal. Even if it's "the right thing to do", many people who hold information that someone with power wants kept secret will decide that their own well being is more important. Anonymous sources are the only way such information can come out, and if the person the source talks to isn't allowed to keep the source secret, anonymous sources become impossible.
On the balance, I'm pretty sure that the value of anonymous sources to a free society outweighs the value of enforced revealing of sources to a lawful society. I am nonetheless troubled by justifying shielding them under the banner of freedom of the press. For one thing, it seems pretty far removed from what I understand freedom of the press to mean, and for another, it opens up a messy gray area of who is "the press" and therefore entitled to shield a source. In the real world, being stuck with the Constitution we have, the freedom of the press justification is probably the best Constitutional argument we have, and if the right isn't anchored in the Constitution it's fragile at best. I find it much more interesting, though, to ponder what we might find in an ideal world.
As I write this, I feel that no one should be compelled to testify if they feel that their testimony would put themselves or anyone else they feel an obligation toward at unacceptable risk of illegal retaliation. A person who has information shouldn't be afraid that if they reveal they know anything, they can be forced to tell everything, knowing that someone will suffer. A person who wants to blow the whistle but feels threatened should be allowed to trust someone to be a conduit for an anonymous source. At the same time, the rules against hearsay evidence need to be relaxed, so that evidence of the form "person X whom I know and trust revealed thus-and-such to me. Person X would be at risk if I revealed his identity," would be allowed in court. Any trier of fact with enough judgment to weigh evidence should implicitly recognize that hearsay evidence is generally less credible than direct testimony, but we make most of our decisions in everyday life on the basis of hearsay, so it's insane that it is banned in court. If hearsay were permitted, there would be less pressure to reveal those anonymous sources.
At the risk of digressing too far to maintain any coherence at all, I will note that I realize that my promotion of hearsay evidence is in conflict with the Constitutional guarantee that the accused may confront the witnesses against him. I've long been troubled by this guarantee as well; while it is a noble goal to protect the accused against a case made up by a corrupt state, the privilege of confronting witnesses has always struck me as guaranteeing the powerful the right to intimidate witnesses to avoid prosecution.
So: Any thoughts about reporters with anonymous sources, or more general issues of who should be compelled to testify?