Slate: "How Deep is CIA Cover?" (Plame Damage)

Click here for the full article. Some excerpts (underlines at end mine):

Nonofficial cover. NOCs (the word rhymes with "rocks") are the most covert CIA operatives. They typically work abroad without diplomatic protection (often they pretend to work for some commercial enterprise). If these spies are caught, there's no guarantee that the United States would admit their true identities. When using official cover could put a spy's life and work at risk, NOC is the only alternative.

Why is it such a big deal that someone outed Valerie Plame? For starters, it's a felony. And Plame was also reportedly a NOC with years of experience investigating weapons of mass destruction. If this is true, her discovery could compromise intelligence operations she was involved with around the world, which would explain why she maintained her nonofficial cover even when she was back in the United States. "Hard target" countries like China and North Korea often keep records of every known meeting between Americans and their scientists and officials. Almost certainly, those lists would have been frantically reviewed when Plame's identity was revealed, and any sources she recruited could have been exposed.

actual damages that have resulted from the "outing". If so, then this can facilitate the need for a special investigation counsel.

This explains why the outing was so dangerous to our informants.