Because she refused to reveal her source in the Plame game. She said this today:
In her seven-minute statement to Hogan, Miller said she "is not above the law" but that journalists must be trusted to keep sources secret. "If journalists cannot be trusted to guarantee confidentiality, then there cannot be a free press."
"I do not take our freedom for granted. I never have and I never will," she said, recalling a four-month stint as an embedded reporter covering the early days of the war in Iraq in 2003. If the military can do their job in Iraq, she said, "surely I can face prison to defend a free press."
Ye-e-es. But didn't her source try to do something not quite legal by contacting her? Does the freedom of the press extend to illegal acts? And when was "a free press" useful as a way for the administration to disseminate false information (as happened earlier in Miller's articles about Iraq) or as a way to punish someone who criticized the administration (Joseph Wilson). It seems to me that the idea of a free press is important because it allows the free criticism of the powers-that-be. In this case something almost the opposite seems to have happened, and Ms. Miller seems to go to prison to protect the government. But I admit that the issue is complicated.