Assume the worst - Valerie Plame's identity was TOP SECRET (it wasn't of course but we are just pretending - just like we're the MSM.)
Then Tenet (who is cleared for TOP SECRET) telling Cheney (who is cleared for TOP SECRET) who then tells Libby (who is cleared for TOP SECRET) in an area that is cleared for TOP SECRET meetings (like the White House) is certainly no crime.
If Plame was covert, her identity would be above Top Secret and on a need-to-know basis. Top Secret clearance is very common in the USG.