There is more to this. When it is revealed that you were a NOC, foreign intelligence services begin combing back over your life, examining every relationship you had. Anyone you came into contact with becomes suspect. Sometimes, in some countries, becoming suspect can cost you your life. Revealing the identity of a NOC can be a matter of life and death -- frequently, of people no one has ever heard of or will ever hear of again.
In short, a NOC owes things to his country, and his country owes things to the NOC. We have no idea what Valerie Plame told her family or friends about her work. It may be that she herself broke the rules, revealing that she once worked as a NOC. We can't know that, because we don't know whether she received authorization from the CIA to say things after her own identity was blown by others. She might have been irresponsible, or she might have engaged in damage control. We just don't know.
What we do know is this. In the course of events, reporters contacted two senior officials in the White House -- Rove and Libby. Under the least-damaging scenario we have heard, the reporters already knew that Plame had worked as a NOC. Rove and Libby, at this point, were obligated to say, at the very least, that they could neither confirm nor deny the report. In fact, their duty would have been quite a bit more: Their job was to lie like crazy to mislead the reporters. Rove and Libby had top security clearances and were senior White House officials. It was their sworn duty, undertaken when they accepted their security clearance, to build a "bodyguard of lies" -- in Churchill's phrase -- around the truth concerning U.S. intelligence capabilities.
Why the Plame Affair is far more important than no talent ass clowns like Boortz would have you believe.