Just to be clear - I don't support sending journalists to prison to coerce them in to testifying. As I said, my father is a journalist, and I certainly don't want to see him sent to prison.
That said, while journalists have been yelling about how we non-journalists "don't get it" that a principle is at stake here, journalists don't seem to get that a very serious crime was comitted in the Plame case. Moreover, it was comitted using the legal protections which journalists are afforded.
Some have compared the Plame/Miller affair to the Skokie case, where Illinois Nazis had their right to assemble defended by the ACLU and the Supreme Court.
[Blues Brothers]I Hate Illinois Nazis.[/Blues Brothers]
That said, I think the Skokie analogy is wrong. Rather, a better example would be the Amadou Diallo shooting in New York. Police, like journalists, are afforded certain legal protections to do their jobs, because society recognizes that their jobs serve a greater purpose - cops are allowed to use lethal force in certain situations, reporters are allowed to keep sources anonymous. But what do we do when those legal protections have obviously been misused?
If you think the proper response to the Diallo shooting (or any example of police misconduct) is to let the police responsible go without any investigation, or to allow the police to interfere and refuse to cooperate with an investigation, then I can see why you might think Miller deserves to go free. She almost certainly has information pertaining to this crime, and is refusing to cooperate. Like journalists are doing today, police have regularly warned that any prosecution of their crimes will lead to their jobs being poorly done - i.e. less law enforcement. Those threats have been hollow. Honest journalism will continue.
It's also worth noting that, like the Diallo case, people have almost certainly died because of Robert Novak's actions. This was a gross misuse of a reporter's privilege, as bad as any police shooting. I can honestly see why some journalists are worried - this affair will change the way reporting is done in the US, and I hope for the better. If it leads to journalists being less giddy about getting anonymous leaks used to smear political opponents, I won't shed a single tear.